diff --git a/app/views/projects/mattermosts/_no_teams.html.haml b/app/views/projects/mattermosts/_no_teams.html.haml
index 605c7f61dee2355566f7451e874298e6172601d5..1bb3642431e56becd9f328c790567758b66afa16 100644
--- a/app/views/projects/mattermosts/_no_teams.html.haml
+++ b/app/views/projects/mattermosts/_no_teams.html.haml
@@ -1,3 +1,6 @@
+= content_for :flash_message do
+  .alert.alert-danger= @teams if @teams.is_a?(String)
+
 %p
   You aren鈥檛 a member of any team on the Mattermost instance at
   %strong= Gitlab.config.mattermost.host
diff --git a/app/views/projects/mattermosts/new.html.haml b/app/views/projects/mattermosts/new.html.haml
index 96b1d2aee61dd72fdaf213af327d565bc29ed59d..82f596da0fea2422e0844a29c3c237bdffc8819f 100644
--- a/app/views/projects/mattermosts/new.html.haml
+++ b/app/views/projects/mattermosts/new.html.haml
@@ -2,7 +2,7 @@
   .inline.pull-right
     = custom_icon('mattermost_logo', size: 48)
   %h3 Install Mattermost Command
-  - if @teams.empty?
+  - if @teams.is_a?(String) || @teams.empty?
     = render 'no_teams'
   - else
     = render 'team_selection'
diff --git a/spec/features/projects/services/mattermost_slash_command_spec.rb b/spec/features/projects/services/mattermost_slash_command_spec.rb
index 86a07b2c679cef209b3bade257591a918581c5ef..6737b85e0d18ea0232200dcf33d1743fc4a81309 100644
--- a/spec/features/projects/services/mattermost_slash_command_spec.rb
+++ b/spec/features/projects/services/mattermost_slash_command_spec.rb
@@ -99,6 +99,15 @@ feature 'Setup Mattermost slash commands', feature: true do
       expect(select_element.all('option').count).to eq(3)
     end
 
+    it 'shows an error alert with the error message if there is an error requesting teams' do
+      allow_any_instance_of(MattermostSlashCommandsService).to receive(:list_teams) { 'test mattermost error message' }
+
+      click_link 'Add to Mattermost'
+
+      expect(page).to have_selector('.alert')
+      expect(page).to have_content('test mattermost error message')
+    end
+
     def stub_teams(count: 0)
       teams = create_teams(count)