diff --git a/client/src/app/features/search/apis/search-api.ts b/client/src/app/features/search/apis/search-api.ts
index 26c119a..14912aa 100644
--- a/client/src/app/features/search/apis/search-api.ts
+++ b/client/src/app/features/search/apis/search-api.ts
@@ -1,5 +1,6 @@
 import type {
   ApiWorldHeritageDto,
+  CriteriaCode,
   ListResult,
   Pagination,
   StudyRegion,
@@ -16,6 +17,8 @@ export type SearchParams = {
   category?: string;
   yearInscribedFrom?: number;
   yearInscribedTo?: number;
+  isEndangered?: boolean;
+  criteria?: readonly CriteriaCode[];
   currentPage?: number;
   perPage?: number;
 };
@@ -72,6 +75,10 @@ export const createSearchApi = ({ apiBase, fetchImpl = fetch }: SearchApiDeps) =
     if (category) queryParams.set("category", category);
     if (yearInscribedFrom) queryParams.set("year_inscribed_from", yearInscribedFrom);
     if (yearInscribedTo) queryParams.set("year_inscribed_to", yearInscribedTo);
+    if (params.isEndangered === true) queryParams.set("is_endangered", "true");
+    if (params.criteria && params.criteria.length > 0) {
+      queryParams.set("criteria", params.criteria.join(","));
+    }
     if (params.currentPage != null) queryParams.set("current_page", String(params.currentPage));
     if (params.perPage != null) queryParams.set("per_page", String(params.perPage));
 
diff --git a/client/src/app/features/search/components/SearchResultsPage.tsx b/client/src/app/features/search/components/SearchResultsPage.tsx
index 911e3fc..5915e8f 100644
--- a/client/src/app/features/search/components/SearchResultsPage.tsx
+++ b/client/src/app/features/search/components/SearchResultsPage.tsx
@@ -7,6 +7,8 @@ import { HeritageCard } from "@features/top/cards/HeritageCard";
 import { Pagination } from "@features/top/components/Pagination.tsx";
 import { BreadcrumbList } from "@shared/components/BreadcrumbList.tsx";
 import { SearchResultMapComponent } from "@features/search/components/SearchResultMapComponent.tsx";
+import { LocaleToggle } from "@shared/locale/LocaleToggle.tsx";
+import { useText } from "@shared/locale/ui-text.ts";
 
 type Props = {
   header?: ReactNode;
@@ -31,6 +33,7 @@ export default function SearchResultsPage({
   onPageChange,
   onBackToAllSites,
 }: Props) {
+  const text = useText();
   return (
     <main className="mx-auto max-w-7xl px-4 py-12">
       <div className="sticky top-0 z-20 -mx-4 border-b border-zinc-200 bg-white/95 px-4 py-3 backdrop-blur">
@@ -69,11 +72,12 @@ export default function SearchResultsPage({
                   h-9 rounded-xl border border-zinc-200 bg-white px-3 text-xs font-semibold text-zinc-700
                   shadow-sm transition hover:bg-zinc-50
                 "
-                aria-label="Back to all sites"
+                aria-label={text.backToAllSites}
               >
-                Back to all sites
+                {text.backToAllSites}
               </button>
             ) : null}
+            <LocaleToggle />
           </div>
         </div>
       </div>
@@ -87,7 +91,7 @@ export default function SearchResultsPage({
 
         {items.length === 0 ? (
           <div className="py-20 text-center">
-            <p className="text-sm text-zinc-600">No sites found.</p>
+            <p className="text-sm text-zinc-600">{text.noSitesFound}</p>
           </div>
         ) : (
           <ul className="grid list-none grid-cols-1 gap-6 p-0 md:grid-cols-2 lg:grid-cols-3">
diff --git a/client/src/app/features/search/containers/__tests__/search-heritage-container.test.tsx b/client/src/app/features/search/containers/__tests__/search-heritage-container.test.tsx
index 62a1154..88eb303 100644
--- a/client/src/app/features/search/containers/__tests__/search-heritage-container.test.tsx
+++ b/client/src/app/features/search/containers/__tests__/search-heritage-container.test.tsx
@@ -39,6 +39,8 @@ type SearchValues = {
   keyword: string;
   yearInscribedFrom: string;
   yearInscribedTo: string;
+  isEndangered: boolean;
+  criteria: string[];
 };
 
 type HeritageSubHeaderProps = {
@@ -144,6 +146,8 @@ const makeParsedParams = (overrides: Partial<HeritageSearchParams> = {}): Herita
   category: null,
   year_inscribed_from: null,
   year_inscribed_to: null,
+  is_endangered: null,
+  criteria: [],
   current_page: 1,
   per_page: 30,
   order: "asc",
@@ -203,6 +207,8 @@ describe("TopPageContainer", () => {
         keyword: "Kyoto",
         yearInscribedFrom: "",
         yearInscribedTo: "",
+        isEndangered: false,
+        criteria: [],
       });
     });
 
@@ -252,6 +258,8 @@ describe("TopPageContainer", () => {
       category: "Cultural",
       year_inscribed_from: 1990,
       year_inscribed_to: null,
+      is_endangered: null,
+      criteria: [],
       current_page: 1,
       per_page: 30,
       order: "asc",
diff --git a/client/src/app/features/search/containers/search-heritage-form-container.tsx b/client/src/app/features/search/containers/search-heritage-form-container.tsx
index 9ea2740..1d1ee6c 100644
--- a/client/src/app/features/search/containers/search-heritage-form-container.tsx
+++ b/client/src/app/features/search/containers/search-heritage-form-container.tsx
@@ -36,6 +36,8 @@ const toSearchValues = (params: HeritageSearchParams): SearchValues => ({
   keyword: params.search_query ?? "",
   yearInscribedFrom: params.year_inscribed_from !== null ? String(params.year_inscribed_from) : "",
   yearInscribedTo: params.year_inscribed_to !== null ? String(params.year_inscribed_to) : "",
+  isEndangered: params.is_endangered === true,
+  criteria: params.criteria,
 });
 
 export function SearchHeritageFormContainer() {
@@ -71,6 +73,8 @@ export function SearchHeritageFormContainer() {
         keyword: query.keyword ?? draft.keyword,
         yearInscribedFrom: query.yearInscribedFrom ?? draft.yearInscribedFrom,
         yearInscribedTo: query.yearInscribedTo ?? draft.yearInscribedTo,
+        isEndangered: query.isEndangered ?? draft.isEndangered,
+        criteria: query.criteria ?? draft.criteria,
       };
 
       const nextParams: HeritageSearchParams = {
@@ -80,17 +84,27 @@ export function SearchHeritageFormContainer() {
         category: toCategoryOrNull(merged.category),
         year_inscribed_from: toSearchYearOrNull(merged.yearInscribedFrom),
         year_inscribed_to: toSearchYearOrNull(merged.yearInscribedTo),
+        is_endangered: merged.isEndangered ? true : null,
+        criteria: merged.criteria,
         current_page: 1,
         per_page: params.per_page ?? DEFAULT_TOP_PER_PAGE,
         order: params.order ?? DEFAULT_ORDER,
         country: null,
       };
 
-      const search = serializeHeritageSearchParams(nextParams);
+      const baseSearch = serializeHeritageSearchParams(nextParams);
+      const currentLang = new URLSearchParams(location.search).get("lang");
+      const finalParams = new URLSearchParams(
+        baseSearch.startsWith("?") ? baseSearch.slice(1) : baseSearch,
+      );
+      if (currentLang === "ja") finalParams.set("lang", "ja");
+      const finalQueryString = finalParams.toString();
+      const search = finalQueryString ? `?${finalQueryString}` : "";
+
       navigate({ pathname: "/heritages/results", search }, { replace: false });
       setDraft(merged);
     },
-    [draft, navigate, params.per_page, params.order],
+    [draft, navigate, params.per_page, params.order, location.search],
   );
 
   return <HeritageSubHeader value={draft} onChange={handleChange} onSubmit={handleSubmit} />;
diff --git a/client/src/app/features/search/containers/search-heritage-result-container.tsx b/client/src/app/features/search/containers/search-heritage-result-container.tsx
index f81144f..41a5c52 100644
--- a/client/src/app/features/search/containers/search-heritage-result-container.tsx
+++ b/client/src/app/features/search/containers/search-heritage-result-container.tsx
@@ -50,7 +50,9 @@ const hasSearchParams = (params: HeritageSearchParams): boolean =>
   params.region !== null ||
   params.category !== null ||
   params.year_inscribed_from !== null ||
-  params.year_inscribed_to !== null;
+  params.year_inscribed_to !== null ||
+  params.is_endangered === true ||
+  params.criteria.length > 0;
 
 const toDraftValues = (params: HeritageSearchParams): SearchValues => ({
   region: params.region ?? "",
@@ -58,6 +60,8 @@ const toDraftValues = (params: HeritageSearchParams): SearchValues => ({
   keyword: params.search_query ?? "",
   yearInscribedFrom: params.year_inscribed_from !== null ? String(params.year_inscribed_from) : "",
   yearInscribedTo: params.year_inscribed_to !== null ? String(params.year_inscribed_to) : "",
+  isEndangered: params.is_endangered === true,
+  criteria: params.criteria,
 });
 
 const toSearchParams = (draft: SearchValues): HeritageSearchParams => ({
@@ -67,6 +71,8 @@ const toSearchParams = (draft: SearchValues): HeritageSearchParams => ({
   category: draft.category || null,
   year_inscribed_from: draft.yearInscribedFrom ? Number(draft.yearInscribedFrom) : null,
   year_inscribed_to: draft.yearInscribedTo ? Number(draft.yearInscribedTo) : null,
+  is_endangered: draft.isEndangered ? true : null,
+  criteria: draft.criteria,
   current_page: 1,
 });
 
@@ -76,8 +82,19 @@ const mergeDraft = (currentDraft: SearchValues, partial: Partial<SearchValues>):
   keyword: partial.keyword ?? currentDraft.keyword,
   yearInscribedFrom: partial.yearInscribedFrom ?? currentDraft.yearInscribedFrom,
   yearInscribedTo: partial.yearInscribedTo ?? currentDraft.yearInscribedTo,
+  isEndangered: partial.isEndangered ?? currentDraft.isEndangered,
+  criteria: partial.criteria ?? currentDraft.criteria,
 });
 
+// 現在の URL に lang=ja があれば、遷移先 search にも持たせる (en はデフォルトなので付けない)
+const preserveLang = (nextSearch: string, currentSearch: string): string => {
+  const currentLang = new URLSearchParams(currentSearch).get("lang");
+  if (currentLang !== "ja") return nextSearch;
+  const params = new URLSearchParams(nextSearch.startsWith("?") ? nextSearch.slice(1) : nextSearch);
+  params.set("lang", "ja");
+  return `?${params.toString()}`;
+};
+
 function useHeritageSearchDraft(params: HeritageSearchParams) {
   const [draft, setDraft] = React.useState<SearchValues>(() => toDraftValues(params));
 
@@ -121,9 +138,10 @@ export function SearchHeritageResultsContainer(): React.ReactElement {
 
   const handleClickItem = React.useCallback(
     (id: number) => {
-      navigate(`/heritages/${id}`);
+      const search = preserveLang("", location.search);
+      navigate(`/heritages/${id}${search}`);
     },
-    [navigate],
+    [navigate, location.search],
   );
 
   const handlePageChange = React.useCallback(
@@ -133,7 +151,7 @@ export function SearchHeritageResultsContainer(): React.ReactElement {
         current_page: page,
       };
 
-      const search = serializeHeritageSearchParams(nextParams);
+      const search = preserveLang(serializeHeritageSearchParams(nextParams), location.search);
 
       navigate(
         {
@@ -143,14 +161,14 @@ export function SearchHeritageResultsContainer(): React.ReactElement {
         { replace: false },
       );
     },
-    [navigate, location.pathname, params],
+    [navigate, location.pathname, location.search, params],
   );
 
   const handleSubmit = React.useCallback(
     (partial: Partial<SearchValues>) => {
       const nextDraft = mergeDraft(draft, partial);
       const nextParams = toSearchParams(nextDraft);
-      const search = serializeHeritageSearchParams(nextParams);
+      const search = preserveLang(serializeHeritageSearchParams(nextParams), location.search);
 
       navigate(
         {
@@ -162,13 +180,14 @@ export function SearchHeritageResultsContainer(): React.ReactElement {
 
       setDraft(nextDraft);
     },
-    [draft, navigate, setDraft],
+    [draft, navigate, setDraft, location.search],
   );
 
   // Hooks must be called at the top level before any early returns.
   const handleBackToAllSites = React.useCallback(() => {
-    navigate("/heritages", { replace: true });
-  }, [navigate]);
+    const search = preserveLang("", location.search);
+    navigate(`/heritages${search}`, { replace: true });
+  }, [navigate, location.search]);
 
   const header = (
     <HeritageSubHeader value={draft} onChange={handleChange} onSubmit={handleSubmit} />
diff --git a/client/src/app/features/search/hooks/__tests__/use-search-heritage-query-test.ts b/client/src/app/features/search/hooks/__tests__/use-search-heritage-query-test.ts
index b783b1a..e38eb43 100644
--- a/client/src/app/features/search/hooks/__tests__/use-search-heritage-query-test.ts
+++ b/client/src/app/features/search/hooks/__tests__/use-search-heritage-query-test.ts
@@ -101,6 +101,8 @@ const makeParams = (overrides: Partial<HeritageSearchParams> = {}): HeritageSear
   category: null,
   year_inscribed_from: null,
   year_inscribed_to: null,
+  is_endangered: null,
+  criteria: [],
   current_page: 1,
   per_page: 30,
   order: null,
diff --git a/client/src/app/features/search/hooks/use-search-heritage-query.ts b/client/src/app/features/search/hooks/use-search-heritage-query.ts
index ed96cde..d9d1b28 100644
--- a/client/src/app/features/search/hooks/use-search-heritage-query.ts
+++ b/client/src/app/features/search/hooks/use-search-heritage-query.ts
@@ -14,6 +14,8 @@ const toSearchParams = (params: HeritageSearchParams): SearchParams => ({
   category: params.category ?? undefined,
   yearInscribedFrom: params.year_inscribed_from ?? undefined,
   yearInscribedTo: params.year_inscribed_to ?? undefined,
+  isEndangered: params.is_endangered === true ? true : undefined,
+  criteria: params.criteria.length > 0 ? params.criteria : undefined,
   currentPage: params.current_page,
   perPage: params.per_page,
 });
diff --git a/client/src/app/features/search/mapper/__tests__/search-heritages.params.test.ts b/client/src/app/features/search/mapper/__tests__/search-heritages.params.test.ts
new file mode 100644
index 0000000..a86d26b
--- /dev/null
+++ b/client/src/app/features/search/mapper/__tests__/search-heritages.params.test.ts
@@ -0,0 +1,124 @@
+import { describe, it, expect } from "@jest/globals";
+import {
+  parseHeritageSearchParams,
+  serializeHeritageSearchParams,
+} from "../search-heritages.params.ts";
+import { DEFAULT_HERITAGE_SEARCH_PARAMS } from "../search-heritage.types.ts";
+import type { HeritageSearchParams } from "../../../../../domain/types.ts";
+
+const baseParams = (overrides: Partial<HeritageSearchParams> = {}): HeritageSearchParams => ({
+  ...DEFAULT_HERITAGE_SEARCH_PARAMS,
+  ...overrides,
+});
+
+describe("parseHeritageSearchParams", () => {
+  it("is_endangered=true is parsed as true", () => {
+    const params = parseHeritageSearchParams("?is_endangered=true");
+    expect(params.is_endangered).toBe(true);
+  });
+
+  it("is_endangered=false is treated as no filter (null)", () => {
+    const params = parseHeritageSearchParams("?is_endangered=false");
+    expect(params.is_endangered).toBeNull();
+  });
+
+  it("missing is_endangered defaults to null", () => {
+    const params = parseHeritageSearchParams("?region=Asia");
+    expect(params.is_endangered).toBeNull();
+  });
+
+  it("garbage is_endangered values fall back to null", () => {
+    const params = parseHeritageSearchParams("?is_endangered=banana");
+    expect(params.is_endangered).toBeNull();
+  });
+});
+
+describe("serializeHeritageSearchParams", () => {
+  it("emits is_endangered=true when params.is_endangered is true", () => {
+    const queryString = serializeHeritageSearchParams(baseParams({ is_endangered: true }));
+    expect(queryString).toContain("is_endangered=true");
+  });
+
+  it("omits is_endangered when null", () => {
+    const queryString = serializeHeritageSearchParams(baseParams({ is_endangered: null }));
+    expect(queryString).not.toContain("is_endangered");
+  });
+
+  it("omits is_endangered when false", () => {
+    const queryString = serializeHeritageSearchParams(baseParams({ is_endangered: false }));
+    expect(queryString).not.toContain("is_endangered");
+  });
+});
+
+describe("round-trip", () => {
+  it("preserves is_endangered=true through serialize -> parse", () => {
+    const queryString = serializeHeritageSearchParams(baseParams({ is_endangered: true }));
+    const parsed = parseHeritageSearchParams(queryString);
+    expect(parsed.is_endangered).toBe(true);
+  });
+
+  it("preserves is_endangered=null through serialize -> parse", () => {
+    const queryString = serializeHeritageSearchParams(baseParams({ is_endangered: null }));
+    const parsed = parseHeritageSearchParams(queryString);
+    expect(parsed.is_endangered).toBeNull();
+  });
+});
+
+describe("parseHeritageSearchParams (criteria)", () => {
+  it("parses comma-separated criteria values", () => {
+    const params = parseHeritageSearchParams("?criteria=ii,iv");
+    expect(params.criteria).toStrictEqual(["ii", "iv"]);
+  });
+
+  it("missing criteria defaults to []", () => {
+    const params = parseHeritageSearchParams("?region=Asia");
+    expect(params.criteria).toStrictEqual([]);
+  });
+
+  it("empty criteria value defaults to []", () => {
+    const params = parseHeritageSearchParams("?criteria=");
+    expect(params.criteria).toStrictEqual([]);
+  });
+
+  it("filters out invalid codes", () => {
+    const params = parseHeritageSearchParams("?criteria=ii,xx,iv");
+    expect(params.criteria).toStrictEqual(["ii", "iv"]);
+  });
+
+  it("dedupes and sorts by CRITERIA order", () => {
+    const params = parseHeritageSearchParams("?criteria=v,ii,ii,i");
+    expect(params.criteria).toStrictEqual(["i", "ii", "v"]);
+  });
+});
+
+describe("serializeHeritageSearchParams (criteria)", () => {
+  it("emits criteria as comma-separated when non-empty", () => {
+    const queryString = serializeHeritageSearchParams(baseParams({ criteria: ["ii", "iv"] }));
+    expect(queryString).toContain("criteria=ii%2Civ");
+  });
+
+  it("omits criteria when empty", () => {
+    const queryString = serializeHeritageSearchParams(baseParams({ criteria: [] }));
+    expect(queryString).not.toContain("criteria");
+  });
+});
+
+describe("round-trip (criteria)", () => {
+  it("preserves single value", () => {
+    const queryString = serializeHeritageSearchParams(baseParams({ criteria: ["iii"] }));
+    const parsed = parseHeritageSearchParams(queryString);
+    expect(parsed.criteria).toStrictEqual(["iii"]);
+  });
+
+  it("preserves multiple values in canonical order", () => {
+    const queryString = serializeHeritageSearchParams(baseParams({ criteria: ["v", "ii", "i"] }));
+    const parsed = parseHeritageSearchParams(queryString);
+    expect(parsed.criteria).toStrictEqual(["i", "ii", "v"]);
+  });
+
+  it("preserves empty array", () => {
+    const queryString = serializeHeritageSearchParams(baseParams({ criteria: [] }));
+    const parsed = parseHeritageSearchParams(queryString);
+    expect(parsed.criteria).toStrictEqual([]);
+  });
+});
diff --git a/client/src/app/features/search/mapper/search-heritage.types.ts b/client/src/app/features/search/mapper/search-heritage.types.ts
index bccf21e..a8daff6 100644
--- a/client/src/app/features/search/mapper/search-heritage.types.ts
+++ b/client/src/app/features/search/mapper/search-heritage.types.ts
@@ -7,6 +7,8 @@ export const DEFAULT_HERITAGE_SEARCH_PARAMS: HeritageSearchParams = {
   category: null,
   year_inscribed_from: null,
   year_inscribed_to: null,
+  is_endangered: null,
+  criteria: [],
   current_page: 1,
   per_page: 30,
   order: ID_SORT_OPTIONS.ASC,
diff --git a/client/src/app/features/search/mapper/search-heritages.params.ts b/client/src/app/features/search/mapper/search-heritages.params.ts
index 8ce00d1..0750718 100644
--- a/client/src/app/features/search/mapper/search-heritages.params.ts
+++ b/client/src/app/features/search/mapper/search-heritages.params.ts
@@ -1,10 +1,11 @@
 import type {
   Category,
+  CriteriaCode,
   HeritageSearchParams,
   IdSortOption,
   StudyRegion,
 } from "../../../../domain/types.ts";
-import { CATEGORIES, STUDY_REGIONS } from "../../../../domain/types.ts";
+import { CATEGORIES, CRITERIA, STUDY_REGIONS } from "../../../../domain/types.ts";
 import { DEFAULT_HERITAGE_SEARCH_PARAMS as defaultSearchParams } from "./search-heritage.types.ts";
 
 const toNullIfEmpty = (value: string | null): string | null => {
@@ -58,6 +59,27 @@ const toOrderOrNull = (value: string | null): IdSortOption | null => {
   return isIdSortOption(trimmed) ? trimmed : null;
 };
 
+// "true" だけ true。それ以外 (空 / 不正値 / "false") は null = フィルタなし扱い。
+const toEndangeredOrNull = (value: string | null): boolean | null => {
+  const trimmed = toNullIfEmpty(value);
+  if (trimmed == null) return null;
+  return trimmed === "true" ? true : null;
+};
+
+const isCriteriaCode = (value: string): value is CriteriaCode =>
+  (CRITERIA as readonly string[]).includes(value);
+
+// comma-separated を CriteriaCode[] にデコード。重複除去 + CRITERIA 順に正規化、不正値は捨てる。
+const toCriteriaCodes = (value: string | null): CriteriaCode[] => {
+  if (value == null) return [];
+  const parts = value
+    .split(",")
+    .map((s) => s.trim())
+    .filter((s) => s.length > 0);
+  const unique = Array.from(new Set(parts)).filter(isCriteriaCode);
+  return unique.sort((a, b) => CRITERIA.indexOf(a) - CRITERIA.indexOf(b));
+};
+
 export function parseHeritageSearchParams(search: string): HeritageSearchParams {
   const searchParams = new URLSearchParams(search);
 
@@ -88,6 +110,11 @@ export function parseHeritageSearchParams(search: string): HeritageSearchParams
 
   const order = toOrderOrNull(searchParams.get("order")) ?? defaultSearchParams.order;
 
+  const is_endangered =
+    toEndangeredOrNull(searchParams.get("is_endangered")) ?? defaultSearchParams.is_endangered;
+
+  const criteria = toCriteriaCodes(searchParams.get("criteria"));
+
   return {
     search_query,
     country,
@@ -95,6 +122,8 @@ export function parseHeritageSearchParams(search: string): HeritageSearchParams
     category,
     year_inscribed_from,
     year_inscribed_to,
+    is_endangered,
+    criteria,
     current_page,
     per_page,
     order,
@@ -138,6 +167,16 @@ export function serializeHeritageSearchParams(params: HeritageSearchParams): str
     searchParams.set("order", params.order);
   }
 
+  // 危機遺産: true のときだけ URL に乗せる (false / null は省略 = no filter)
+  if (params.is_endangered === true) {
+    searchParams.set("is_endangered", "true");
+  }
+
+  // criteria: 非空のときだけ comma-separated で URL に乗せる
+  if (params.criteria.length > 0) {
+    searchParams.set("criteria", params.criteria.join(","));
+  }
+
   const queryString = searchParams.toString();
   return queryString ? `?${queryString}` : "";
 }
diff --git a/client/src/app/features/top/components/HeritageSearchForm.tsx b/client/src/app/features/top/components/HeritageSearchForm.tsx
index 47bc0dd..1c2e454 100644
--- a/client/src/app/features/top/components/HeritageSearchForm.tsx
+++ b/client/src/app/features/top/components/HeritageSearchForm.tsx
@@ -2,8 +2,10 @@ import { useState } from "react";
 import SearchIcon from "@mui/icons-material/Search";
 import {
   CATEGORIES,
+  CRITERIA,
   STUDY_REGIONS,
   type Category,
+  type CriteriaCode,
   type SearchValues,
   type StudyRegion,
 } from "../../../../domain/types.ts";
@@ -18,6 +20,8 @@ type Props = {
     keyword?: string;
     yearInscribedFrom?: string;
     yearInscribedTo?: string;
+    isEndangered?: boolean;
+    criteria?: CriteriaCode[];
   }) => void;
 };
 
@@ -40,6 +44,8 @@ export function HeritageSearchForm({ value, onChange, onSubmit }: Props) {
     keyword: value?.keyword ?? "",
     yearInscribedFrom: value?.yearInscribedFrom ?? "",
     yearInscribedTo: value?.yearInscribedTo ?? "",
+    isEndangered: value?.isEndangered ?? false,
+    criteria: value?.criteria ?? [],
   });
 
   const searchValues = value ?? internal;
@@ -50,6 +56,14 @@ export function HeritageSearchForm({ value, onChange, onSubmit }: Props) {
     onChange?.(next);
   };
 
+  const toggleCriterion = (code: CriteriaCode) => {
+    const current = searchValues.criteria;
+    const next = current.includes(code)
+      ? current.filter((c) => c !== code)
+      : [...current, code].sort((a, b) => CRITERIA.indexOf(a) - CRITERIA.indexOf(b));
+    set({ criteria: next });
+  };
+
   const submit = () => {
     onSubmit?.({
       region: searchValues.region || undefined,
@@ -57,6 +71,8 @@ export function HeritageSearchForm({ value, onChange, onSubmit }: Props) {
       keyword: searchValues.keyword.trim() || undefined,
       yearInscribedFrom: searchValues.yearInscribedFrom || undefined,
       yearInscribedTo: searchValues.yearInscribedTo || undefined,
+      isEndangered: searchValues.isEndangered || undefined,
+      criteria: searchValues.criteria.length > 0 ? searchValues.criteria : undefined,
     });
   };
 
@@ -122,6 +138,47 @@ export function HeritageSearchForm({ value, onChange, onSubmit }: Props) {
         </div>
       </div>
 
+      {/* Criteria チップ (multi-select) */}
+      <div className="px-4 pt-3 pb-2 border-b border-zinc-100">
+        <div className="text-[11px] font-semibold text-zinc-400 mb-2">{text.criteria}</div>
+        <div className="flex flex-wrap gap-2">
+          {CRITERIA.map((code) => {
+            const isActive = searchValues.criteria.includes(code);
+            return (
+              <button
+                key={code}
+                type="button"
+                onClick={() => toggleCriterion(code)}
+                aria-pressed={isActive}
+                className={`
+                  px-3 py-1.5 rounded-full text-xs font-semibold border transition-all
+                  ${
+                    isActive
+                      ? "bg-zinc-900 text-white border-zinc-900"
+                      : "bg-white text-zinc-600 border-zinc-200 hover:border-zinc-400"
+                  }
+                `}
+              >
+                {code}
+              </button>
+            );
+          })}
+        </div>
+      </div>
+
+      {/* 危機遺産フラグ */}
+      <div className="px-4 py-2 border-b border-zinc-100">
+        <label className="inline-flex items-center gap-2 text-xs font-semibold text-zinc-700 cursor-pointer">
+          <input
+            type="checkbox"
+            checked={searchValues.isEndangered}
+            onChange={(e) => set({ isEndangered: e.target.checked })}
+            className="h-4 w-4 rounded border-zinc-300 text-rose-600 focus:ring-rose-400"
+          />
+          {text.endangeredOnly}
+        </label>
+      </div>
+
       {/* Year + Keyword + Submit */}
       <div className="divide-y divide-zinc-100 sm:divide-y-0 sm:flex sm:items-stretch">
         {/* Year */}
diff --git a/client/src/app/features/top/components/heritage-detail/HeritageDetailLayout.tsx b/client/src/app/features/top/components/heritage-detail/HeritageDetailLayout.tsx
index f9cbd06..5ed6de8 100644
--- a/client/src/app/features/top/components/heritage-detail/HeritageDetailLayout.tsx
+++ b/client/src/app/features/top/components/heritage-detail/HeritageDetailLayout.tsx
@@ -19,6 +19,8 @@ const DEFAULT_SEARCH: SearchValues = {
   keyword: "",
   yearInscribedFrom: "",
   yearInscribedTo: "",
+  isEndangered: false,
+  criteria: [],
 };
 
 const formatCriteriaInline = (criteria: string[] | undefined) =>
@@ -114,6 +116,8 @@ export function HeritageDetailLayout({ item }: { item: WorldHeritageDetailVm })
     if (next.category) params.set("category", next.category);
     if (next.yearInscribedFrom) params.set("year_inscribed_from", next.yearInscribedFrom);
     if (next.yearInscribedTo) params.set("year_inscribed_to", next.yearInscribedTo);
+    if (next.isEndangered) params.set("is_endangered", "true");
+    if (next.criteria.length > 0) params.set("criteria", next.criteria.join(","));
 
     navigate(`/heritages/results?${params.toString()}`);
   };
diff --git a/client/src/app/features/top/components/heritage-detail/HeritageSubHeader.tsx b/client/src/app/features/top/components/heritage-detail/HeritageSubHeader.tsx
index f855d6d..5fea2bb 100644
--- a/client/src/app/features/top/components/heritage-detail/HeritageSubHeader.tsx
+++ b/client/src/app/features/top/components/heritage-detail/HeritageSubHeader.tsx
@@ -30,6 +30,8 @@ export function HeritageSubHeader({ value, onChange, onSubmit }: Props): React.J
     keyword: value?.keyword ?? "",
     yearInscribedFrom: value?.yearInscribedFrom ?? "",
     yearInscribedTo: value?.yearInscribedTo ?? "",
+    isEndangered: value?.isEndangered ?? false,
+    criteria: value?.criteria ?? [],
   });
 
   const current = value ?? internal;
diff --git a/client/src/domain/types.ts b/client/src/domain/types.ts
index f874aba..17e8179 100644
--- a/client/src/domain/types.ts
+++ b/client/src/domain/types.ts
@@ -182,6 +182,8 @@ export interface HeritageSearchParams {
   category: Category | null;
   year_inscribed_from: number | null;
   year_inscribed_to: number | null;
+  is_endangered: boolean | null;
+  criteria: CriteriaCode[];
   current_page: number;
   per_page: number;
   order: IdSortOption | null;
@@ -198,4 +200,6 @@ export type SearchValues = {
   keyword: string;
   yearInscribedFrom: string;
   yearInscribedTo: string;
+  isEndangered: boolean;
+  criteria: CriteriaCode[];
 };
diff --git a/client/src/locals/en/ui.json b/client/src/locals/en/ui.json
index 81f8f5e..9986355 100644
--- a/client/src/locals/en/ui.json
+++ b/client/src/locals/en/ui.json
@@ -30,6 +30,9 @@
   "reload": "Reload",
   "sortById": "Sort by ID",
   "all": "All",
+  "endangeredOnly": "Endangered only",
+  "backToAllSites": "Back to all sites",
+  "noSitesFound": "No sites found.",
   "keyword": "Keyword",
   "keywordPlaceholder": "Name / Country",
   "yearFrom": "From",
diff --git a/client/src/locals/ja/ui.json b/client/src/locals/ja/ui.json
index 7ba0b60..7490e36 100644
--- a/client/src/locals/ja/ui.json
+++ b/client/src/locals/ja/ui.json
@@ -30,6 +30,9 @@
   "reload": "再読み込み",
   "sortById": "ID で並び替え",
   "all": "すべて",
+  "endangeredOnly": "危機遺産のみ表示",
+  "backToAllSites": "一覧に戻る",
+  "noSitesFound": "該当する遺産はありません。",
   "keyword": "キーワード",
   "keywordPlaceholder": "名称・国名",
   "yearFrom": "から",