diff --git a/packages/backend/src/server/api/endpoints/mute/create.ts b/packages/backend/src/server/api/endpoints/mute/create.ts
index 01af0d656..683a9bd25 100644
--- a/packages/backend/src/server/api/endpoints/mute/create.ts
+++ b/packages/backend/src/server/api/endpoints/mute/create.ts
@@ -5,6 +5,7 @@ import { publishUserEvent } from '@/services/stream.js';
 import define from '@/server/api/define.js';
 import { ApiError } from '@/server/api/error.js';
 import { getUser } from '@/server/api/common/getters.js';
+import { createMute } from '@/services/mute/create.js';
 
 export const meta = {
 	tags: ['account'],
@@ -51,19 +52,7 @@ export default define(meta, paramDef, async (ps, user) => {
 		return;
 	}
 
-	// Create mute
-	await Mutings.insert({
-		id: genId(),
-		createdAt: new Date(),
-		expiresAt: ps.expiresAt ? new Date(ps.expiresAt) : null,
-		muterId: muter.id,
-		muteeId: mutee.id,
-	} as Muting);
+	const expiresAt = ps.expiresAt ? new Date(ps.expiresAt) : null;
 
-	publishUserEvent(user.id, 'mute', mutee);
-
-	NoteWatchings.delete({
-		userId: muter.id,
-		noteUserId: mutee.id,
-	});
+	await createMute(muter, mutee, expiresAt);
 });
diff --git a/packages/backend/src/services/mute/create.ts b/packages/backend/src/services/mute/create.ts
new file mode 100644
index 000000000..d12d76fdb
--- /dev/null
+++ b/packages/backend/src/services/mute/create.ts
@@ -0,0 +1,33 @@
+import { genId } from '@/misc/gen-id.js';
+import { Mutings, NoteWatchings } from '@/models/index.js';
+import { Muting } from '@/models/entities/muting.js';
+import { publishUserEvent } from '@/services/stream.js';
+import { User } from '@/models/entities/user.js';
+
+export async function createMute(muter: User, mutee: User, expiresAt: Date | null): Promise<void> {
+	if (expiresAt && ps.expiresAt <= Date.now()) {
+		return;
+	}
+
+	await Promise.all([
+		// Create mute
+		Mutings.insert({
+			id: genId(),
+			createdAt: new Date(),
+			expiresAt,
+			muterId: muter.id,
+			muteeId: mutee.id,
+		} as Muting),
+		removeWatchings(muter, mutee),
+		removeWatchings(mutee, muter),
+	]);
+
+	publishUserEvent(user.id, 'mute', mutee);
+});
+
+async function removeWatchings(watcher: User, watched: User): Promise<void> {
+	await NoteWatchings.delete({
+		userId: watcher.id,
+		noteUserId: watched.id,
+	});
+}