diff --git a/packages/backend/src/core/ChatService.ts b/packages/backend/src/core/ChatService.ts
index 46062e1572..334a798483 100644
--- a/packages/backend/src/core/ChatService.ts
+++ b/packages/backend/src/core/ChatService.ts
@@ -248,11 +248,11 @@ export class ChatService {
 	public async readUserChatMessage(
 		readerId: MiUser['id'],
 		senderId: MiUser['id'],
-	) {
+	): Promise<void> {
 		const redisPipeline = this.redisClient.pipeline();
 		redisPipeline.del(`newChatMessageExists:${readerId}:${senderId}`);
 		redisPipeline.srem(`newChatMessagesExists:${readerId}`, `user:${senderId}`);
-		redisPipeline.exec();
+		await redisPipeline.exec();
 	}
 
 	@bindThis
@@ -467,6 +467,7 @@ export class ChatService {
 
 	@bindThis
 	public async hasUnreadMessages(userId: MiUser['id']) {
-		// TODO
+		const card = await this.redisClient.scard(`newChatMessagesExists:${userId}`);
+		return card > 0;
 	}
 }
diff --git a/packages/backend/src/core/GlobalEventService.ts b/packages/backend/src/core/GlobalEventService.ts
index 2a62b41f33..a0b90d62fc 100644
--- a/packages/backend/src/core/GlobalEventService.ts
+++ b/packages/backend/src/core/GlobalEventService.ts
@@ -74,6 +74,7 @@ export interface MainEventTypes {
 	unreadNotification: Packed<'Notification'>;
 	readAllAntennas: undefined;
 	unreadAntenna: MiAntenna;
+	newChatMessage: Packed<'ChatMessage'>;
 	readAllAnnouncements: undefined;
 	myTokenRegenerated: undefined;
 	signin: {
diff --git a/packages/backend/src/models/json-schema/user.ts b/packages/backend/src/models/json-schema/user.ts
index 8147cc36a1..b10430782b 100644
--- a/packages/backend/src/models/json-schema/user.ts
+++ b/packages/backend/src/models/json-schema/user.ts
@@ -545,6 +545,10 @@ export const packedMeDetailedOnlySchema = {
 			type: 'boolean',
 			nullable: false, optional: false,
 		},
+		hasUnreadChatMessages: {
+			type: 'boolean',
+			nullable: false, optional: false,
+		},
 		hasUnreadNotification: {
 			type: 'boolean',
 			nullable: false, optional: false,
diff --git a/packages/backend/test/e2e/users.ts b/packages/backend/test/e2e/users.ts
index b91d294d09..f82d4c6a30 100644
--- a/packages/backend/test/e2e/users.ts
+++ b/packages/backend/test/e2e/users.ts
@@ -133,6 +133,7 @@ describe('ユーザー', () => {
 			hasUnreadAnnouncement: user.hasUnreadAnnouncement,
 			hasUnreadAntenna: user.hasUnreadAntenna,
 			hasUnreadChannel: user.hasUnreadChannel,
+			hasUnreadChatMessages: user.hasUnreadChatMessages,
 			hasUnreadNotification: user.hasUnreadNotification,
 			unreadNotificationsCount: user.unreadNotificationsCount,
 			hasPendingReceivedFollowRequest: user.hasPendingReceivedFollowRequest,
@@ -371,6 +372,7 @@ describe('ユーザー', () => {
 		assert.strictEqual(response.hasUnreadAnnouncement, false);
 		assert.strictEqual(response.hasUnreadAntenna, false);
 		assert.strictEqual(response.hasUnreadChannel, false);
+		assert.strictEqual(response.hasUnreadChatMessages, false);
 		assert.strictEqual(response.hasUnreadNotification, false);
 		assert.strictEqual(response.unreadNotificationsCount, 0);
 		assert.strictEqual(response.hasPendingReceivedFollowRequest, false);
diff --git a/packages/frontend/src/boot/main-boot.ts b/packages/frontend/src/boot/main-boot.ts
index 1ee07658fb..7be5cf1f21 100644
--- a/packages/frontend/src/boot/main-boot.ts
+++ b/packages/frontend/src/boot/main-boot.ts
@@ -511,6 +511,11 @@ export async function mainBoot() {
 			sound.playMisskeySfx('antenna');
 		});
 
+		main.on('newChatMessage', () => {
+			updateCurrentAccountPartial({ hasUnreadChatMessages: true });
+			sound.playMisskeySfx('chat');
+		});
+
 		main.on('readAllAnnouncements', () => {
 			updateCurrentAccountPartial({ hasUnreadAnnouncement: false });
 		});
diff --git a/packages/frontend/src/navbar.ts b/packages/frontend/src/navbar.ts
index d3a8560403..894df83721 100644
--- a/packages/frontend/src/navbar.ts
+++ b/packages/frontend/src/navbar.ts
@@ -114,6 +114,7 @@ export const navbarItemDef = reactive({
 		title: i18n.ts.chat,
 		icon: 'ti ti-message',
 		to: '/chat',
+		indicated: computed(() => $i != null && $i.hasUnreadChatMessages),
 	},
 	achievements: {
 		title: i18n.ts.achievements,
diff --git a/packages/misskey-js/etc/misskey-js.api.md b/packages/misskey-js/etc/misskey-js.api.md
index 6507eb7681..f258a2474a 100644
--- a/packages/misskey-js/etc/misskey-js.api.md
+++ b/packages/misskey-js/etc/misskey-js.api.md
@@ -626,6 +626,7 @@ export type Channels = {
             readAllUnreadSpecifiedNotes: () => void;
             readAllAntennas: () => void;
             unreadAntenna: (payload: Antenna) => void;
+            newChatMessage: (payload: ChatMessage) => void;
             readAllAnnouncements: () => void;
             myTokenRegenerated: () => void;
             signin: (payload: Signin) => void;
@@ -3480,8 +3481,8 @@ type V2AdminEmojiListResponse = operations['v2___admin___emoji___list']['respons
 //
 // src/entities.ts:50:2 - (ae-forgotten-export) The symbol "ModerationLogPayloads" needs to be exported by the entry point index.d.ts
 // src/streaming.ts:57:3 - (ae-forgotten-export) The symbol "ReconnectingWebSocket" needs to be exported by the entry point index.d.ts
-// src/streaming.types.ts:220:4 - (ae-forgotten-export) The symbol "ReversiUpdateKey" needs to be exported by the entry point index.d.ts
-// src/streaming.types.ts:230:4 - (ae-forgotten-export) The symbol "ReversiUpdateSettings" needs to be exported by the entry point index.d.ts
+// src/streaming.types.ts:222:4 - (ae-forgotten-export) The symbol "ReversiUpdateKey" needs to be exported by the entry point index.d.ts
+// src/streaming.types.ts:232:4 - (ae-forgotten-export) The symbol "ReversiUpdateSettings" needs to be exported by the entry point index.d.ts
 
 // (No @packageDocumentation comment for this package)
 
diff --git a/packages/misskey-js/src/autogen/types.ts b/packages/misskey-js/src/autogen/types.ts
index c40da6bfc8..6e0346b935 100644
--- a/packages/misskey-js/src/autogen/types.ts
+++ b/packages/misskey-js/src/autogen/types.ts
@@ -3914,6 +3914,7 @@ export type components = {
       unreadAnnouncements: components['schemas']['Announcement'][];
       hasUnreadAntenna: boolean;
       hasUnreadChannel: boolean;
+      hasUnreadChatMessages: boolean;
       hasUnreadNotification: boolean;
       hasPendingReceivedFollowRequest: boolean;
       unreadNotificationsCount: number;
diff --git a/packages/misskey-js/src/streaming.types.ts b/packages/misskey-js/src/streaming.types.ts
index 26a50f9fa4..05b2d28ec8 100644
--- a/packages/misskey-js/src/streaming.types.ts
+++ b/packages/misskey-js/src/streaming.types.ts
@@ -1,5 +1,6 @@
 import {
 	Antenna,
+	ChatMessage,
 	DriveFile,
 	DriveFolder,
 	Note,
@@ -53,6 +54,7 @@ export type Channels = {
 			readAllUnreadSpecifiedNotes: () => void;
 			readAllAntennas: () => void;
 			unreadAntenna: (payload: Antenna) => void;
+			newChatMessage: (payload: ChatMessage) => void;
 			readAllAnnouncements: () => void;
 			myTokenRegenerated: () => void;
 			signin: (payload: Signin) => void;