diff --git a/app/assets/javascripts/components/features/compose/components/compose_form.jsx b/app/assets/javascripts/components/features/compose/components/compose_form.jsx
index 273ebd83f3..9edc01ed76 100644
--- a/app/assets/javascripts/components/features/compose/components/compose_form.jsx
+++ b/app/assets/javascripts/components/features/compose/components/compose_form.jsx
@@ -36,6 +36,8 @@ const ComposeForm = React.createClass({
     in_reply_to: ImmutablePropTypes.map,
     media_count: React.PropTypes.number,
     me: React.PropTypes.number,
+    needsPrivacyWarning: React.PropTypes.bool,
+    mentionedDomains: React.PropTypes.array.isRequired,
     onChange: React.PropTypes.func.isRequired,
     onSubmit: React.PropTypes.func.isRequired,
     onCancelReply: React.PropTypes.func.isRequired,
@@ -117,16 +119,29 @@ const ComposeForm = React.createClass({
   },
 
   render () {
-    const { intl }  = this.props;
-    let replyArea   = '';
-    let publishText = '';
-    const disabled  = this.props.is_submitting || this.props.is_uploading;
+    const { intl, needsPrivacyWarning, mentionedDomains } = this.props;
+    const disabled = this.props.is_submitting || this.props.is_uploading;
+
+    let replyArea      = '';
+    let publishText    = '';
+    let privacyWarning = '';
+    let reply_to_other = !!this.props.in_reply_to && (this.props.in_reply_to.getIn(['account', 'id']) !== this.props.me);
 
     if (this.props.in_reply_to) {
       replyArea = <ReplyIndicator status={this.props.in_reply_to} onCancel={this.props.onCancelReply} />;
     }
 
-    let reply_to_other = !!this.props.in_reply_to && (this.props.in_reply_to.getIn(['account', 'id']) !== this.props.me);
+    if (needsPrivacyWarning) {
+      privacyWarning = (
+        <div className='compose-form__warning'>
+          <FormattedMessage
+            id='compose_form.privacy_disclaimer'
+            defaultMessage='Your private status will be delivered to mentioned users on {domains}. Do you trust {domainsCount, plural, one {that server} other {those servers}} to not leak your status?'
+            values={{ domains: <strong>{mentionedDomains.join(', ')}</strong>, domainsCount: mentionedDomains.length }}
+          />
+        </div>
+      );
+    }
 
     if (this.props.private) {
       publishText = <span><i className='fa fa-lock' /> {intl.formatMessage(messages.publish)}</span>;
@@ -142,6 +157,7 @@ const ComposeForm = React.createClass({
           </div>
         </Collapsable>
 
+        {privacyWarning}
         {replyArea}
 
         <AutosuggestTextarea
diff --git a/app/assets/javascripts/components/features/compose/containers/compose_form_container.jsx b/app/assets/javascripts/components/features/compose/containers/compose_form_container.jsx
index c027875cdc..2671ea618b 100644
--- a/app/assets/javascripts/components/features/compose/containers/compose_form_container.jsx
+++ b/app/assets/javascripts/components/features/compose/containers/compose_form_container.jsx
@@ -19,6 +19,8 @@ const makeMapStateToProps = () => {
   const getStatus = makeGetStatus();
 
   const mapStateToProps = function (state, props) {
+    const mentionedUsernamesWithDomains = state.getIn(['compose', 'text']).match(/(?:^|[^\/\w])@([a-z0-9_]+@[a-z0-9\.\-]+)/ig);
+
     return {
       text: state.getIn(['compose', 'text']),
       suggestion_token: state.getIn(['compose', 'suggestion_token']),
@@ -34,6 +36,8 @@ const makeMapStateToProps = () => {
       in_reply_to: getStatus(state, state.getIn(['compose', 'in_reply_to'])),
       media_count: state.getIn(['compose', 'media_attachments']).size,
       me: state.getIn(['compose', 'me']),
+      needsPrivacyWarning: state.getIn(['compose', 'private']) && mentionedUsernamesWithDomains !== null,
+      mentionedDomains: mentionedUsernamesWithDomains !== null ? [...new Set(mentionedUsernamesWithDomains.map(item => item.split('@')[2]))] : []
     };
   };
 
diff --git a/app/assets/javascripts/components/locales/en.jsx b/app/assets/javascripts/components/locales/en.jsx
index ac1c1a7d53..95962fd738 100644
--- a/app/assets/javascripts/components/locales/en.jsx
+++ b/app/assets/javascripts/components/locales/en.jsx
@@ -41,6 +41,7 @@ const en = {
   "compose_form.sensitive": "Mark media as sensitive",
   "compose_form.spoiler": "Hide text behind warning",
   "compose_form.private": "Mark as private",
+  "compose_form.privacy_disclaimer": "Your private status will be delivered to mentioned users on {domains}. Do you trust {domainsCount, plural, one {that server} other {those servers}} to not leak your status?",
   "compose_form.unlisted": "Do not display in public timeline",
   "navigation_bar.edit_profile": "Edit profile",
   "navigation_bar.preferences": "Preferences",
diff --git a/app/assets/stylesheets/components.scss b/app/assets/stylesheets/components.scss
index f0948b0f39..247ea3132e 100644
--- a/app/assets/stylesheets/components.scss
+++ b/app/assets/stylesheets/components.scss
@@ -78,6 +78,21 @@
   color: $color1;
 }
 
+.compose-form__warning {
+  color: $color2;
+  margin-bottom: 15px;
+  border: 1px solid $color3;
+  padding: 8px 10px;
+  border-radius: 4px;
+  font-size: 12px;
+  font-weight: 400;
+
+  strong {
+    color: $color5;
+    font-weight: 500;
+  }
+}
+
 .compose-form__label {
   display: block;
   line-height: 24px;