diff --git a/internal/files/yaml.go b/internal/files/yaml.go
index 317071f..33283cb 100644
--- a/internal/files/yaml.go
+++ b/internal/files/yaml.go
@@ -68,6 +68,14 @@ func UpdateYAMLFile(cfg VersionFileConfig, currentVersion, newVersion string) er
 		// Embedded version found - replace just the version portion
 		oldValue = valueAtPath
 		newValue = strings.Replace(valueAtPath, oldVersionStr, newVersionStr, 1)
+	} else if embeddedVersion := findEmbeddedVersion(valueAtPath, cfg.Prefix); embeddedVersion != "" {
+		// Value contains an embedded version, but it doesn't match currentVersion
+		// This indicates a version mismatch that should be fixed before releasing
+		return fmt.Errorf("version mismatch in %s at path %s: "+
+			"expected to find %q but found %q in value %q. "+
+			"This usually means the file was not updated in a previous release. "+
+			"Please manually update the version in this file to %q before running releaseo",
+			cfg.File, cfg.Path, oldVersionStr, embeddedVersion, valueAtPath, oldVersionStr)
 	} else {
 		// No embedded version - replace the entire value (original behavior)
 		oldValue = valueAtPath
@@ -168,6 +176,33 @@ func surgicalReplace(data []byte, oldValue, newValue string) ([]byte, error) {
 	return nil, fmt.Errorf("could not find value %q to replace", oldValue)
 }
 
+// findEmbeddedVersion looks for a version pattern in the value and returns it if found.
+// It detects patterns like ":v1.2.3", ":1.2.3", or prefix followed by semver at end of string.
+// Returns empty string if no embedded version is detected.
+func findEmbeddedVersion(value, prefix string) string {
+	// Pattern to match versions: optional prefix + semver (major.minor.patch with optional prerelease)
+	// Looks for versions after ":" (common in image tags) or at end of string
+	patterns := []string{
+		// Image tag style: repo:v1.2.3 or repo:1.2.3
+		`:` + regexp.QuoteMeta(prefix) + `(\d+\.\d+\.\d+(?:-[a-zA-Z0-9.]+)?)`,
+		// Version at end of string with prefix
+		regexp.QuoteMeta(prefix) + `(\d+\.\d+\.\d+(?:-[a-zA-Z0-9.]+)?)$`,
+	}
+
+	for _, pattern := range patterns {
+		re := regexp.MustCompile(pattern)
+		if matches := re.FindStringSubmatch(value); matches != nil {
+			// Return the full match including prefix (reconstruct it)
+			if strings.HasPrefix(matches[0], ":") {
+				return matches[0][1:] // Remove leading ":"
+			}
+			return matches[0]
+		}
+	}
+
+	return ""
+}
+
 // convertToYAMLPath converts a dot notation path to YAML path format.
 // Examples:
 //
diff --git a/internal/files/yaml_test.go b/internal/files/yaml_test.go
index c87768a..6eaca72 100644
--- a/internal/files/yaml_test.go
+++ b/internal/files/yaml_test.go
@@ -328,6 +328,143 @@ func TestUpdateYAMLFile_PreservesQuotes(t *testing.T) {
 	}
 }
 
+func TestUpdateYAMLFile_VersionMismatch(t *testing.T) {
+	t.Parallel()
+
+	tests := []struct {
+		name           string
+		input          string
+		config         VersionFileConfig
+		currentVersion string
+		newVersion     string
+		wantErrContain string
+	}{
+		{
+			name: "image tag version mismatch",
+			input: `operator:
+  image: ghcr.io/stacklok/toolhive/operator:v0.8.1
+`,
+			config:         VersionFileConfig{Path: "operator.image", Prefix: "v"},
+			currentVersion: "0.8.2",
+			newVersion:     "0.8.3",
+			wantErrContain: "version mismatch",
+		},
+		{
+			name: "image tag version mismatch shows found version",
+			input: `toolhiveRunnerImage: ghcr.io/stacklok/toolhive/proxyrunner:v0.7.1
+`,
+			config:         VersionFileConfig{Path: "toolhiveRunnerImage", Prefix: "v"},
+			currentVersion: "0.8.0",
+			newVersion:     "0.8.1",
+			wantErrContain: "v0.7.1",
+		},
+		{
+			name: "image tag version mismatch shows expected version",
+			input: `image: registry.io/app:v1.0.0
+`,
+			config:         VersionFileConfig{Path: "image", Prefix: "v"},
+			currentVersion: "2.0.0",
+			newVersion:     "2.0.1",
+			wantErrContain: "v2.0.0",
+		},
+		{
+			name: "version mismatch without prefix",
+			input: `image: myregistry.io/app:1.0.0
+`,
+			config:         VersionFileConfig{Path: "image"},
+			currentVersion: "2.0.0",
+			newVersion:     "2.0.1",
+			wantErrContain: "version mismatch",
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			t.Parallel()
+
+			tmpPath := createTempFile(t, tt.input, "yaml-test-*.yaml")
+
+			cfg := tt.config
+			cfg.File = tmpPath
+
+			err := UpdateYAMLFile(cfg, tt.currentVersion, tt.newVersion)
+			if err == nil {
+				t.Error("UpdateYAMLFile() expected error for version mismatch")
+				return
+			}
+
+			if !strings.Contains(err.Error(), tt.wantErrContain) {
+				t.Errorf("UpdateYAMLFile() error should contain %q, got: %v", tt.wantErrContain, err)
+			}
+		})
+	}
+}
+
+func TestFindEmbeddedVersion(t *testing.T) {
+	t.Parallel()
+
+	tests := []struct {
+		name   string
+		value  string
+		prefix string
+		want   string
+	}{
+		{
+			name:   "image tag with v prefix",
+			value:  "ghcr.io/stacklok/toolhive/operator:v0.8.1",
+			prefix: "v",
+			want:   "v0.8.1",
+		},
+		{
+			name:   "image tag without prefix",
+			value:  "myregistry.io/app:1.0.0",
+			prefix: "",
+			want:   "1.0.0",
+		},
+		{
+			name:   "image tag with prerelease",
+			value:  "registry.io/app:v1.0.0-alpha.1",
+			prefix: "v",
+			want:   "v1.0.0-alpha.1",
+		},
+		{
+			name:   "simple version at end",
+			value:  "v1.2.3",
+			prefix: "v",
+			want:   "v1.2.3",
+		},
+		{
+			name:   "no version found",
+			value:  "some-random-string",
+			prefix: "v",
+			want:   "",
+		},
+		{
+			name:   "no version in plain text",
+			value:  "hello world",
+			prefix: "",
+			want:   "",
+		},
+		{
+			name:   "version in URL path (not tag)",
+			value:  "https://example.com/v1/api",
+			prefix: "v",
+			want:   "",
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			t.Parallel()
+
+			got := findEmbeddedVersion(tt.value, tt.prefix)
+			if got != tt.want {
+				t.Errorf("findEmbeddedVersion(%q, %q) = %q, want %q", tt.value, tt.prefix, got, tt.want)
+			}
+		})
+	}
+}
+
 func TestUpdateYAMLFile_PreservesComments(t *testing.T) {
 	t.Parallel()