diff --git a/app/assets/javascripts/admin/models/admin-user.js.es6 b/app/assets/javascripts/admin/models/admin-user.js.es6
index a4341d09d..8bbd72900 100644
--- a/app/assets/javascripts/admin/models/admin-user.js.es6
+++ b/app/assets/javascripts/admin/models/admin-user.js.es6
@@ -264,6 +264,7 @@ const AdminUser = Discourse.User.extend({
   },
 
   unblock() {
+    this.set('blockingUser', true);
     return Discourse.ajax('/admin/users/' + this.id + '/unblock', {
       type: 'PUT'
     }).then(function() {
@@ -275,14 +276,33 @@ const AdminUser = Discourse.User.extend({
   },
 
   block() {
-    return Discourse.ajax('/admin/users/' + this.id + '/block', {
-      type: 'PUT'
-    }).then(function() {
-      window.location.reload();
-    }).catch(function(e) {
-      var error = I18n.t('admin.user.block_failed', { error: "http: " + e.status + " - " + e.body });
-      bootbox.alert(error);
-    });
+    const user = this,
+          message = I18n.t("admin.user.block_confirm");
+
+    const performBlock = function() {
+      user.set('blockingUser', true);
+      return Discourse.ajax('/admin/users/' + user.id + '/block', {
+        type: 'PUT'
+      }).then(function() {
+        window.location.reload();
+      }).catch(function(e) {
+        var error = I18n.t('admin.user.block_failed', { error: "http: " + e.status + " - " + e.body });
+        bootbox.alert(error);
+        user.set('blockingUser', false);
+      });
+    };
+
+    const buttons = [{
+      "label": I18n.t("composer.cancel"),
+      "class": "cancel",
+      "link":  true
+    }, {
+      "label": '<i class="fa fa-exclamation-triangle"></i>' + I18n.t('admin.user.block_accept'),
+      "class": "btn btn-danger",
+      "callback": function() { performBlock(); }
+    }];
+
+    bootbox.dialog(message, buttons, { "classes": "delete-user-modal" });
   },
 
   sendActivationEmail() {
diff --git a/app/assets/javascripts/admin/templates/user-index.hbs b/app/assets/javascripts/admin/templates/user-index.hbs
index 32190c967..b868854e8 100644
--- a/app/assets/javascripts/admin/templates/user-index.hbs
+++ b/app/assets/javascripts/admin/templates/user-index.hbs
@@ -327,13 +327,21 @@
     <div class='field'>{{i18n 'admin.user.blocked'}}</div>
     <div class='value'>{{model.blocked}}</div>
     <div class='controls'>
-      {{#if model.blocked}}
-        <button class='btn' {{action "unblock" target="content"}}>
-          {{fa-icon "thumbs-o-up"}}
-          {{i18n 'admin.user.unblock'}}
-        </button>
-        {{i18n 'admin.user.block_explanation'}}
-      {{/if}}
+      {{#conditional-loading-spinner size="small" condition=model.blockingUser}}
+        {{#if model.blocked}}
+          <button class='btn' {{action "unblock" target="content"}}>
+            {{fa-icon "thumbs-o-up"}}
+            {{i18n 'admin.user.unblock'}}
+          </button>
+          {{i18n 'admin.user.block_explanation'}}
+        {{else}}
+          <button class='btn' {{action "block" target="content"}}>
+            {{fa-icon "ban"}}
+            {{i18n 'admin.user.block'}}
+          </button>
+          {{i18n 'admin.user.block_explanation'}}
+        {{/if}}
+      {{/conditional-loading-spinner}}
     </div>
   </div>
 </section>
diff --git a/config/locales/client.en.yml b/config/locales/client.en.yml
index 57501ee38..d39f76dfa 100644
--- a/config/locales/client.en.yml
+++ b/config/locales/client.en.yml
@@ -2448,6 +2448,8 @@ en:
         deactivate_failed: "There was a problem deactivating the user."
         unblock_failed: 'There was a problem unblocking the user.'
         block_failed: 'There was a problem blocking the user.'
+        block_confirm: 'Are you sure you want to block this user? They will not be able to create any new topics or posts.'
+        block_accept: 'Yes, block this user'
         deactivate_explanation: "A deactivated user must re-validate their email."
         suspended_explanation: "A suspended user can't log in."
         block_explanation: "A blocked user can't post or start topics."