diff --git a/changelogs/unreleased/api-shared_group_expires-at.yml b/changelogs/unreleased/api-shared_group_expires-at.yml
new file mode 100644
index 00000000000..3d569de65fa
--- /dev/null
+++ b/changelogs/unreleased/api-shared_group_expires-at.yml
@@ -0,0 +1,5 @@
+---
+title: 'API: Add expiration date for shared projects to the project entity'
+merge_request: 21104
+author: Robert Schilling
+type: added
diff --git a/doc/api/groups.md b/doc/api/groups.md
index 87be36cc815..64e0d78788d 100644
--- a/doc/api/groups.md
+++ b/doc/api/groups.md
@@ -351,12 +351,14 @@ Example response:
         {
           "group_id": 4,
           "group_name": "Twitter",
-          "group_access_level": 30
+          "group_access_level": 30,
+          "expires_at": null
         },
         {
           "group_id": 3,
           "group_name": "Gitlab Org",
-          "group_access_level": 10
+          "group_access_level": 10,
+          "expires_at": "2018-08-14"
         }
       ]
     }
diff --git a/lib/api/entities.rb b/lib/api/entities.rb
index 27f28e1df93..864640dcb69 100644
--- a/lib/api/entities.rb
+++ b/lib/api/entities.rb
@@ -91,6 +91,7 @@ module API
         group_link.group.name
       end
       expose :group_access, as: :group_access_level
+      expose :expires_at
     end
 
     class ProjectIdentity < Grape::Entity
diff --git a/spec/factories/project_group_links.rb b/spec/factories/project_group_links.rb
index d5ace9425a0..59c77627ee5 100644
--- a/spec/factories/project_group_links.rb
+++ b/spec/factories/project_group_links.rb
@@ -2,5 +2,6 @@ FactoryBot.define do
   factory :project_group_link do
     project
     group
+    expires_at nil
   end
 end
diff --git a/spec/requests/api/projects_spec.rb b/spec/requests/api/projects_spec.rb
index eb41750bf47..e1b024a39f2 100644
--- a/spec/requests/api/projects_spec.rb
+++ b/spec/requests/api/projects_spec.rb
@@ -914,12 +914,28 @@ describe API::Projects do
         expect(json_response['shared_with_groups'][0]['group_id']).to eq(group.id)
         expect(json_response['shared_with_groups'][0]['group_name']).to eq(group.name)
         expect(json_response['shared_with_groups'][0]['group_access_level']).to eq(link.group_access)
+        expect(json_response['shared_with_groups'][0]['expires_at']).to be_nil
         expect(json_response['only_allow_merge_if_pipeline_succeeds']).to eq(project.only_allow_merge_if_pipeline_succeeds)
         expect(json_response['only_allow_merge_if_all_discussions_are_resolved']).to eq(project.only_allow_merge_if_all_discussions_are_resolved)
         expect(json_response['merge_method']).to eq(project.merge_method.to_s)
         expect(json_response['readme_url']).to eq(project.readme_url)
       end
 
+      it 'returns a group link with expiration date' do
+        group = create(:group)
+        expires_at = 5.days.from_now.to_date
+        link = create(:project_group_link, project: project, group: group, expires_at: expires_at)
+
+        get api("/projects/#{project.id}", user)
+
+        expect(json_response['shared_with_groups']).to be_an Array
+        expect(json_response['shared_with_groups'].length).to eq(1)
+        expect(json_response['shared_with_groups'][0]['group_id']).to eq(group.id)
+        expect(json_response['shared_with_groups'][0]['group_name']).to eq(group.name)
+        expect(json_response['shared_with_groups'][0]['group_access_level']).to eq(link.group_access)
+        expect(json_response['shared_with_groups'][0]['expires_at']).to eq(expires_at.to_s)
+      end
+
       it 'returns a project by path name' do
         get api("/projects/#{project.id}", user)
         expect(response).to have_gitlab_http_status(200)