diff --git a/app/models/form/admin_settings.rb b/app/models/form/admin_settings.rb
index bd7bed3af52961..55909bc0ce98f8 100644
--- a/app/models/form/admin_settings.rb
+++ b/app/models/form/admin_settings.rb
@@ -39,6 +39,7 @@ class Form::AdminSettings
     captcha_enabled
     ng_words
     ng_words_for_stranger_mention
+    stranger_mention_from_local_ng
     hide_local_users_for_anonymous
     post_hash_tags_max
     sensitive_words
@@ -79,6 +80,7 @@ class Form::AdminSettings
     check_lts_version_only
     enable_public_unlisted_visibility
     unlocked_friend
+    stranger_mention_from_local_ng
   ).freeze
 
   UPLOAD_KEYS = %i(
diff --git a/app/services/post_status_service.rb b/app/services/post_status_service.rb
index cdd1aa86747e89..5410323dbb5e42 100644
--- a/app/services/post_status_service.rb
+++ b/app/services/post_status_service.rb
@@ -146,6 +146,7 @@ def process_status!
     @status = @account.statuses.new(status_attributes)
     process_mentions_service.call(@status, limited_type: @status.limited_visibility? ? @limited_scope : '', circle: @circle, save_records: false)
     safeguard_mentions!(@status)
+    validate_status_mentions!
 
     @status.limited_scope = :personal if @status.limited_visibility? && !process_mentions_service.mentions?
 
@@ -208,6 +209,15 @@ def validate_status!
     raise Mastodon::ValidationError, I18n.t('statuses.too_many_hashtags') if Admin::NgWord.hashtag_reject_with_extractor?(@options[:text])
   end
 
+  def validate_status_mentions!
+    raise Mastodon::ValidationError, I18n.t('statuses.contains_ng_words') if mention_to_stranger? && Setting.stranger_mention_from_local_ng && Admin::NgWord.stranger_mention_reject?("#{@options[:spoiler_text]}\n#{@options[:text]}")
+  end
+
+  def mention_to_stranger?
+    @status.mentions.map(&:account).to_a.any? { |mentioned_account| mentioned_account.id != @account && !mentioned_account.following?(@account) } ||
+      (@in_reply_to && @in_reply_to.account.id != @account.id && !@in_reply_to.account.following?(@account))
+  end
+
   def validate_media!
     if @options[:media_ids].blank? || !@options[:media_ids].is_a?(Enumerable)
       @media = []
diff --git a/app/views/admin/ng_words/show.html.haml b/app/views/admin/ng_words/show.html.haml
index 3450135c3c64a3..2a81eec057b1e5 100644
--- a/app/views/admin/ng_words/show.html.haml
+++ b/app/views/admin/ng_words/show.html.haml
@@ -10,6 +10,9 @@
   .fields-group
     = f.input :ng_words_for_stranger_mention, wrapper: :with_label, as: :text, input_html: { rows: 12 }, label: t('admin.ng_words.keywords_for_stranger_mention'), hint: t('admin.ng_words.keywords_for_stranger_mention_hint')
 
+  .fields-group
+    = f.input :stranger_mention_from_local_ng, wrapper: :with_label, as: :boolean, label: t('admin.ng_words.stranger_mention_from_local_ng'), hint: t('admin.ng_words.stranger_mention_from_local_ng_hint')
+
   .fields-group
     = f.input :ng_words, wrapper: :with_label, as: :text, input_html: { rows: 12 }, label: t('admin.ng_words.keywords'), hint: t('admin.ng_words.keywords_hint')
 
diff --git a/config/locales/en.yml b/config/locales/en.yml
index b5e9f348236dc8..747545112824bb 100644
--- a/config/locales/en.yml
+++ b/config/locales/en.yml
@@ -647,6 +647,8 @@ en:
       keywords_for_stranger_mention_hint: Currently this words are checked posts from other servers only.
       keywords_hint: The first character of the line is "?". to use regular expressions
       post_hash_tags_max: Hash tags max for posts
+      stranger_mention_from_local_ng: フォローしていないアカウントへのメンションのNGワードを、ローカルユーザーによる投稿にも適用する
+      stranger_mention_from_local_ng_hint: サーバーの登録が承認制でない場合、あなたのサーバーにもスパムが入り込む可能性があります
       test_error: Testing is returned any errors
       title: NG words and against spams
     relationships:
diff --git a/config/locales/ja.yml b/config/locales/ja.yml
index 98de29324f8366..e0539d21501b7f 100644
--- a/config/locales/ja.yml
+++ b/config/locales/ja.yml
@@ -647,6 +647,8 @@ ja:
       keywords_for_stranger_mention_hint: フォローしていないアカウントへのメンションにのみ適用されます。現状は外部サーバーから来た投稿のみに適用されます
       keywords_hint: 行を「?」で始めると、正規表現が使えます
       post_hash_tags_max: 投稿に設定可能なハッシュタグの最大数
+      stranger_mention_from_local_ng: フォローしていないアカウントへのメンションのNGワードを、ローカルユーザーによる投稿にも適用する
+      stranger_mention_from_local_ng_hint: サーバーの登録が承認制でない場合、あなたのサーバーにもスパムが入り込む可能性があります
       test_error: NGワードのテストに失敗しました。正規表現のミスが含まれているかもしれません
       title: NGワードとスパム
     relationships:
diff --git a/config/settings.yml b/config/settings.yml
index 1fb106e680a2e9..65128db7f0ff7f 100644
--- a/config/settings.yml
+++ b/config/settings.yml
@@ -44,6 +44,7 @@ defaults: &defaults
   check_lts_version_only: true
   enable_public_unlisted_visibility: true
   unlocked_friend: false
+  stranger_mention_from_local_ng: true
 
 development:
   <<: *defaults
diff --git a/spec/services/post_status_service_spec.rb b/spec/services/post_status_service_spec.rb
index f63829f23495e1..adf7e33d8ec9a9 100644
--- a/spec/services/post_status_service_spec.rb
+++ b/spec/services/post_status_service_spec.rb
@@ -436,6 +436,82 @@
     expect(status2.id).to eq status1.id
   end
 
+  describe 'ng word is set' do
+    it 'hit ng words' do
+      account = Fabricate(:account)
+      text = 'ng word test'
+      Form::AdminSettings.new(ng_words: 'test').save
+
+      expect { subject.call(account, text: text) }.to raise_error(Mastodon::ValidationError)
+    end
+
+    it 'not hit ng words' do
+      account = Fabricate(:account)
+      text = 'ng word aiueo'
+      Form::AdminSettings.new(ng_words: 'test').save
+
+      status = subject.call(account, text: text)
+
+      expect(status).to be_persisted
+      expect(status.text).to eq text
+    end
+
+    it 'hit ng words for mention' do
+      account = Fabricate(:account)
+      mentioned = Fabricate(:account, username: 'ohagi', domain: nil)
+      text = 'ng word test @ohagi'
+      Form::AdminSettings.new(ng_words_for_stranger_mention: 'test', stranger_mention_from_local_ng: '1').save
+
+      expect { subject.call(account, text: text) }.to raise_error(Mastodon::ValidationError)
+    end
+
+    it 'hit ng words for mention but local posts are not checked' do
+      account = Fabricate(:account)
+      mentioned = Fabricate(:account, username: 'ohagi', domain: nil)
+      text = 'ng word test @ohagi'
+      Form::AdminSettings.new(ng_words_for_stranger_mention: 'test', stranger_mention_from_local_ng: '0').save
+
+      status = subject.call(account, text: text)
+
+      expect(status).to be_persisted
+      expect(status.text).to eq text
+    end
+
+    it 'hit ng words for mention to follower' do
+      account = Fabricate(:account)
+      mentioned = Fabricate(:account, username: 'ohagi', domain: nil)
+      mentioned.follow!(account)
+      text = 'ng word test @ohagi'
+      Form::AdminSettings.new(ng_words_for_stranger_mention: 'test', stranger_mention_from_local_ng: '1').save
+
+      status = subject.call(account, text: text)
+
+      expect(status).to be_persisted
+      expect(status.text).to eq text
+    end
+
+    it 'hit ng words for reply' do
+      account = Fabricate(:account)
+      text = 'ng word test'
+      Form::AdminSettings.new(ng_words_for_stranger_mention: 'test', stranger_mention_from_local_ng: '1').save
+
+      expect { subject.call(account, text: text, thread: Fabricate(:status)) }.to raise_error(Mastodon::ValidationError)
+    end
+
+    it 'hit ng words for reply to follower' do
+      account = Fabricate(:account)
+      mentioned = Fabricate(:account, username: 'ohagi', domain: nil)
+      mentioned.follow!(account)
+      text = 'ng word test'
+      Form::AdminSettings.new(ng_words_for_stranger_mention: 'test', stranger_mention_from_local_ng: '1').save
+
+      status = subject.call(account, text: text)
+
+      expect(status).to be_persisted
+      expect(status.text).to eq text
+    end
+  end
+
   def create_status_with_options(**options)
     subject.call(Fabricate(:account), options.merge(text: 'test'))
   end