diff --git a/.changeset/cozy-meals-rush.md b/.changeset/cozy-meals-rush.md
new file mode 100644
index 00000000..d776cb97
--- /dev/null
+++ b/.changeset/cozy-meals-rush.md
@@ -0,0 +1,5 @@
+---
+"@labdigital/commercetools-mock": minor
+---
+
+Add basic support for discount codes in the cart repository
diff --git a/src/repositories/cart/actions.ts b/src/repositories/cart/actions.ts
index 4fc62c33..6f818f16 100644
--- a/src/repositories/cart/actions.ts
+++ b/src/repositories/cart/actions.ts
@@ -42,6 +42,7 @@ import type {
 	ProductVariant,
 } from "@commercetools/platform-sdk";
 import type {
+	CartAddDiscountCodeAction,
 	CustomLineItem,
 	DirectDiscount,
 } from "@commercetools/platform-sdk/dist/declarations/src/generated/models/cart";
@@ -61,6 +62,7 @@ import {
 	calculateCartTotalPrice,
 	calculateLineItemTotalPrice,
 	createCustomLineItemFromDraft,
+	createDiscountCodeInfoFromCode,
 	selectPrice,
 } from "./helpers.ts";
 import type { CartRepository } from "./index.ts";
@@ -280,6 +282,25 @@ export class CartUpdateHandler
 		// and prices on related Products have changed in the meanwhile.
 	}
 
+	addDiscountCode(
+		context: RepositoryContext,
+		resource: Writable<Cart>,
+		{ code }: CartAddDiscountCodeAction,
+	) {
+		const info = createDiscountCodeInfoFromCode(
+			context.projectKey,
+			this._storage,
+			code,
+		);
+		if (
+			!resource.discountCodes
+				.map((dc) => dc.discountCode.id)
+				.includes(info.discountCode.id)
+		) {
+			resource.discountCodes.push(info);
+		}
+	}
+
 	removeDiscountCode(
 		context: RepositoryContext,
 		resource: Writable<Cart>,
diff --git a/src/repositories/cart/helpers.ts b/src/repositories/cart/helpers.ts
index d96a036b..5722a9ae 100644
--- a/src/repositories/cart/helpers.ts
+++ b/src/repositories/cart/helpers.ts
@@ -2,12 +2,15 @@ import type {
 	Cart,
 	CustomLineItem,
 	CustomLineItemDraft,
+	DiscountCodeInfo,
+	DiscountCodeNonApplicableError,
 	LineItem,
 	Price,
 	TaxCategory,
 	TaxCategoryReference,
 } from "@commercetools/platform-sdk";
 import { v4 as uuidv4 } from "uuid";
+import { CommercetoolsError } from "#src/exceptions.ts";
 import { calculateTaxedPrice } from "#src/lib/tax.ts";
 import type { AbstractStorage } from "#src/storage/abstract.ts";
 import {
@@ -121,3 +124,29 @@ export const createCustomLineItemFromDraft = (
 		taxedPricePortions: [],
 	};
 };
+
+export const createDiscountCodeInfoFromCode = (
+	projectKey: string,
+	storage: AbstractStorage,
+	code: string,
+): DiscountCodeInfo => {
+	const discountCodes = storage.query(projectKey, "discount-code", {
+		where: `code="${code}"`,
+	});
+	// Does not validate anything besides existence of the DiscountCode object
+	if (discountCodes.count === 0) {
+		throw new CommercetoolsError<DiscountCodeNonApplicableError>({
+			code: "DiscountCodeNonApplicable",
+			message: `The discount code '${code}' was not found.`,
+			reason: "DoesNotExist",
+			discountCode: "nonexistent",
+		});
+	}
+	return {
+		discountCode: {
+			typeId: "discount-code",
+			id: discountCodes.results[0].id,
+		},
+		state: "MatchesCart",
+	};
+};
diff --git a/src/repositories/cart/index.test.ts b/src/repositories/cart/index.test.ts
index 9a65cdd9..8e752828 100644
--- a/src/repositories/cart/index.test.ts
+++ b/src/repositories/cart/index.test.ts
@@ -716,4 +716,36 @@ describe("createShippingInfo", () => {
 		expect(result.taxedPrice!.totalGross.centAmount).toBe(1204);
 		expect(result.taxedPrice!.totalNet.centAmount).toBe(995);
 	});
+
+	test("create cart with discount code", async () => {
+		const code = storage.add("dummy", "discount-code", {
+			...getBaseResourceProperties(),
+			code: "test-1234",
+			cartDiscounts: [],
+			isActive: true,
+			references: [],
+			groups: [],
+		});
+
+		const cart: CartDraft = {
+			country: "NL",
+			currency: "EUR",
+			discountCodes: ["test-1234"],
+		};
+
+		const ctx = { projectKey: "dummy", storeKey: "dummyStore" };
+
+		const result = repository.create(ctx, cart);
+		expect(result.id).toBeDefined();
+
+		expect(result.discountCodes).toEqual([
+			{
+				discountCode: {
+					typeId: "discount-code",
+					id: code.id,
+				},
+				state: "MatchesCart",
+			},
+		]);
+	});
 });
diff --git a/src/repositories/cart/index.ts b/src/repositories/cart/index.ts
index 75208c43..afbf99e4 100644
--- a/src/repositories/cart/index.ts
+++ b/src/repositories/cart/index.ts
@@ -2,6 +2,7 @@ import type {
 	BusinessUnit,
 	Cart,
 	CartDraft,
+	DiscountCodeInfo,
 	GeneralError,
 	InvalidOperationError,
 	LineItem,
@@ -29,6 +30,7 @@ import { CartUpdateHandler } from "./actions.ts";
 import {
 	calculateCartTotalPrice,
 	createCustomLineItemFromDraft,
+	createDiscountCodeInfoFromCode,
 	selectPrice,
 } from "./helpers.ts";
 
@@ -87,6 +89,20 @@ export class CartRepository extends AbstractResourceRepository<"cart"> {
 				),
 			) ?? [];
 
+		// Validate that discount codes exist
+		const discountCodeInfo: DiscountCodeInfo[] = [];
+		if (draft.discountCodes?.length) {
+			draft.discountCodes.forEach((code) => {
+				discountCodeInfo.push(
+					createDiscountCodeInfoFromCode(
+						context.projectKey,
+						this._storage,
+						code,
+					),
+				);
+			});
+		}
+
 		const resource: Writable<Cart> = {
 			...getBaseResourceProperties(),
 			anonymousId: draft.anonymousId,
@@ -106,7 +122,7 @@ export class CartRepository extends AbstractResourceRepository<"cart"> {
 			customerEmail: draft.customerEmail,
 			customLineItems,
 			directDiscounts: [],
-			discountCodes: [],
+			discountCodes: discountCodeInfo,
 			inventoryMode: "None",
 			itemShippingAddresses: [],
 			lineItems,