diff --git a/src/api/endpoints/i/update.ts b/src/api/endpoints/i/update.ts
index 2a5dce64a8..76bad2d156 100644
--- a/src/api/endpoints/i/update.ts
+++ b/src/api/endpoints/i/update.ts
@@ -51,6 +51,11 @@ module.exports = async (params, user, _, isSecure) => new Promise(async (res, re
 	if (isBotErr) return rej('invalid is_bot param');
 	if (isBot != null) user.is_bot = isBot;
 
+	// Get 'auto_watch' parameter
+	const [autoWatch, autoWatchErr] = $(params.auto_watch).optional.boolean().$;
+	if (autoWatchErr) return rej('invalid auto_watch param');
+	if (autoWatch != null) user.settings.auto_watch = autoWatch;
+
 	await User.update(user._id, {
 		$set: {
 			name: user.name,
@@ -58,7 +63,8 @@ module.exports = async (params, user, _, isSecure) => new Promise(async (res, re
 			avatar_id: user.avatar_id,
 			banner_id: user.banner_id,
 			profile: user.profile,
-			is_bot: user.is_bot
+			is_bot: user.is_bot,
+			settings: user.settings
 		}
 	});
 
diff --git a/src/api/endpoints/posts/create.ts b/src/api/endpoints/posts/create.ts
index 57f98fa811..a9d52fd128 100644
--- a/src/api/endpoints/posts/create.ts
+++ b/src/api/endpoints/posts/create.ts
@@ -377,9 +377,9 @@ module.exports = (params, user: IUser, app) => new Promise(async (res, rej) => {
 			});
 
 		// この投稿をWatchする
-		// TODO: ユーザーが「返信したときに自動でWatchする」設定を
-		//       オフにしていた場合はしない
-		watch(user._id, reply);
+		if (user.settings.auto_watch !== false) {
+			watch(user._id, reply);
+		}
 
 		// Add mention
 		addMention(reply.user_id, 'reply');
diff --git a/src/api/endpoints/posts/polls/vote.ts b/src/api/endpoints/posts/polls/vote.ts
index 5a4fd1c268..8222fe5326 100644
--- a/src/api/endpoints/posts/polls/vote.ts
+++ b/src/api/endpoints/posts/polls/vote.ts
@@ -100,9 +100,9 @@ module.exports = (params, user) => new Promise(async (res, rej) => {
 		});
 
 	// この投稿をWatchする
-	// TODO: ユーザーが「投票したときに自動でWatchする」設定を
-	//       オフにしていた場合はしない
-	watch(user._id, post);
+	if (user.settings.auto_watch !== false) {
+		watch(user._id, post);
+	}
 });
 
 function findWithAttr(array, attr, value) {
diff --git a/src/api/endpoints/posts/reactions/create.ts b/src/api/endpoints/posts/reactions/create.ts
index 0b0e0e294d..93d9756d02 100644
--- a/src/api/endpoints/posts/reactions/create.ts
+++ b/src/api/endpoints/posts/reactions/create.ts
@@ -116,7 +116,7 @@ module.exports = (params, user) => new Promise(async (res, rej) => {
 		});
 
 	// この投稿をWatchする
-	// TODO: ユーザーが「リアクションしたときに自動でWatchする」設定を
-	//       オフにしていた場合はしない
-	watch(user._id, post);
+	if (user.settings.auto_watch !== false) {
+		watch(user._id, post);
+	}
 });
diff --git a/src/api/models/user.ts b/src/api/models/user.ts
index 278b949db5..2fea0566ba 100644
--- a/src/api/models/user.ts
+++ b/src/api/models/user.ts
@@ -81,6 +81,8 @@ export type IUser = {
 	keywords: string[];
 	two_factor_secret: string;
 	two_factor_enabled: boolean;
+	client_settings: any;
+	settings: any;
 };
 
 export function init(user): IUser {
diff --git a/src/api/private/signup.ts b/src/api/private/signup.ts
index 19e3314756..1e3e9fb45f 100644
--- a/src/api/private/signup.ts
+++ b/src/api/private/signup.ts
@@ -132,7 +132,9 @@ export default async (req: express.Request, res: express.Response) => {
 			location: null,
 			weight: null
 		},
-		settings: {},
+		settings: {
+			auto_watch: true
+		},
 		client_settings: {
 			home: homeData,
 			show_donation: false
diff --git a/src/web/app/desktop/views/components/settings.vue b/src/web/app/desktop/views/components/settings.vue
index a0ffc4e0aa..0eb18770a5 100644
--- a/src/web/app/desktop/views/components/settings.vue
+++ b/src/web/app/desktop/views/components/settings.vue
@@ -62,6 +62,13 @@
 			</div>
 		</section>
 
+		<section class="notification" v-show="page == 'notification'">
+			<h1>通知</h1>
+			<mk-switch v-model="autoWatch" @change="onChangeAutoWatch" text="投稿の自動ウォッチ">
+				<span>リアクションしたり返信したりした投稿に関する通知を自動的に受け取るようにします。</span>
+			</mk-switch>
+		</section>
+
 		<section class="drive" v-show="page == 'drive'">
 			<h1>%i18n:desktop.tags.mk-settings.drive%</h1>
 			<mk-drive-setting/>
@@ -173,6 +180,7 @@ export default Vue.extend({
 			version,
 			latestVersion: undefined,
 			checkingForUpdate: false,
+			autoWatch: true,
 			enableSounds: localStorage.getItem('enableSounds') == 'true',
 			lang: localStorage.getItem('lang') || '',
 			preventUpdate: localStorage.getItem('preventUpdate') == 'true',
@@ -206,12 +214,21 @@ export default Vue.extend({
 		(this as any).os.getMeta().then(meta => {
 			this.meta = meta;
 		});
+
+		if ((this as any).os.i.settings.auto_watch != null) {
+			this.autoWatch = (this as any).os.i.settings.auto_watch;
+		}
 	},
 	methods: {
 		customizeHome() {
 			this.$router.push('/i/customize-home');
 			this.$emit('done');
 		},
+		onChangeAutoWatch(v) {
+			(this as any).api('i/update', {
+				auto_watch: v
+			});
+		},
 		onChangeShowPostFormOnTopOfTl(v) {
 			(this as any).api('i/update_client_setting', {
 				name: 'showPostFormOnTopOfTl',