diff --git a/changelogs/unreleased/23655-api-group-issues.yml b/changelogs/unreleased/23655-api-group-issues.yml
new file mode 100644
index 00000000000..e19e588d09e
--- /dev/null
+++ b/changelogs/unreleased/23655-api-group-issues.yml
@@ -0,0 +1,4 @@
+---
+title: Fix API group/issues default state filter
+merge_request:
+author: Alexander Randa
diff --git a/lib/api/issues.rb b/lib/api/issues.rb
index fd2674910d2..4dce5dd130a 100644
--- a/lib/api/issues.rb
+++ b/lib/api/issues.rb
@@ -63,14 +63,14 @@ module API
         success Entities::IssueBasic
       end
       params do
-        optional :state, type: String, values: %w[opened closed all], default: 'opened',
+        optional :state, type: String, values: %w[opened closed all], default: 'all',
                          desc: 'Return opened, closed, or all issues'
         use :issues_params
       end
       get ":id/issues" do
         group = find_group!(params[:id])
 
-        issues = find_issues(group_id: group.id, state: params[:state] || 'opened')
+        issues = find_issues(group_id: group.id)
 
         present paginate(issues), with: Entities::IssueBasic, current_user: current_user
       end
diff --git a/lib/api/v3/issues.rb b/lib/api/v3/issues.rb
index 54c6a8060b8..715083fc4f8 100644
--- a/lib/api/v3/issues.rb
+++ b/lib/api/v3/issues.rb
@@ -73,14 +73,14 @@ module API
           success ::API::Entities::Issue
         end
         params do
-          optional :state, type: String, values: %w[opened closed all], default: 'opened',
+          optional :state, type: String, values: %w[opened closed all], default: 'all',
                            desc: 'Return opened, closed, or all issues'
           use :issues_params
         end
         get ":id/issues" do
           group = find_group!(params[:id])
 
-          issues = find_issues(group_id: group.id, state: params[:state] || 'opened', match_all_labels: true)
+          issues = find_issues(group_id: group.id, match_all_labels: true)
 
           present paginate(issues), with: ::API::Entities::Issue, current_user: current_user
         end
diff --git a/spec/requests/api/issues_spec.rb b/spec/requests/api/issues_spec.rb
index 52f68fed2cc..91d6fb83c0b 100644
--- a/spec/requests/api/issues_spec.rb
+++ b/spec/requests/api/issues_spec.rb
@@ -333,8 +333,16 @@ describe API::Issues, api: true  do
     end
     let(:base_url) { "/groups/#{group.id}/issues" }
 
+    it 'returns all group issues (including opened and closed)' do
+      get api(base_url, admin)
+
+      expect(response).to have_http_status(200)
+      expect(json_response).to be_an Array
+      expect(json_response.length).to eq(3)
+    end
+
     it 'returns group issues without confidential issues for non project members' do
-      get api(base_url, non_member)
+      get api("#{base_url}?state=opened", non_member)
 
       expect(response).to have_http_status(200)
       expect(response).to include_pagination_headers
@@ -344,7 +352,7 @@ describe API::Issues, api: true  do
     end
 
     it 'returns group confidential issues for author' do
-      get api(base_url, author)
+      get api("#{base_url}?state=opened", author)
 
       expect(response).to have_http_status(200)
       expect(response).to include_pagination_headers
@@ -353,7 +361,7 @@ describe API::Issues, api: true  do
     end
 
     it 'returns group confidential issues for assignee' do
-      get api(base_url, assignee)
+      get api("#{base_url}?state=opened", assignee)
 
       expect(response).to have_http_status(200)
       expect(response).to include_pagination_headers
@@ -362,7 +370,7 @@ describe API::Issues, api: true  do
     end
 
     it 'returns group issues with confidential issues for project members' do
-      get api(base_url, user)
+      get api("#{base_url}?state=opened", user)
 
       expect(response).to have_http_status(200)
       expect(response).to include_pagination_headers
@@ -371,7 +379,7 @@ describe API::Issues, api: true  do
     end
 
     it 'returns group confidential issues for admin' do
-      get api(base_url, admin)
+      get api("#{base_url}?state=opened", admin)
 
       expect(response).to have_http_status(200)
       expect(response).to include_pagination_headers
@@ -460,7 +468,7 @@ describe API::Issues, api: true  do
     end
 
     it 'returns an array of issues in given milestone' do
-      get api("#{base_url}?milestone=#{group_milestone.title}", user)
+      get api("#{base_url}?state=opened&milestone=#{group_milestone.title}", user)
 
       expect(response).to have_http_status(200)
       expect(response).to include_pagination_headers
diff --git a/spec/requests/api/v3/issues_spec.rb b/spec/requests/api/v3/issues_spec.rb
index 51021eec63c..383871d5c38 100644
--- a/spec/requests/api/v3/issues_spec.rb
+++ b/spec/requests/api/v3/issues_spec.rb
@@ -285,8 +285,16 @@ describe API::V3::Issues, api: true  do
     end
     let(:base_url) { "/groups/#{group.id}/issues" }
 
+    it 'returns all group issues (including opened and closed)' do
+      get v3_api(base_url, admin)
+
+      expect(response).to have_http_status(200)
+      expect(json_response).to be_an Array
+      expect(json_response.length).to eq(3)
+    end
+
     it 'returns group issues without confidential issues for non project members' do
-      get v3_api(base_url, non_member)
+      get v3_api("#{base_url}?state=opened", non_member)
 
       expect(response).to have_http_status(200)
       expect(json_response).to be_an Array
@@ -295,7 +303,7 @@ describe API::V3::Issues, api: true  do
     end
 
     it 'returns group confidential issues for author' do
-      get v3_api(base_url, author)
+      get v3_api("#{base_url}?state=opened", author)
 
       expect(response).to have_http_status(200)
       expect(json_response).to be_an Array
@@ -303,7 +311,7 @@ describe API::V3::Issues, api: true  do
     end
 
     it 'returns group confidential issues for assignee' do
-      get v3_api(base_url, assignee)
+      get v3_api("#{base_url}?state=opened", assignee)
 
       expect(response).to have_http_status(200)
       expect(json_response).to be_an Array
@@ -311,7 +319,7 @@ describe API::V3::Issues, api: true  do
     end
 
     it 'returns group issues with confidential issues for project members' do
-      get v3_api(base_url, user)
+      get v3_api("#{base_url}?state=opened", user)
 
       expect(response).to have_http_status(200)
       expect(json_response).to be_an Array
@@ -319,7 +327,7 @@ describe API::V3::Issues, api: true  do
     end
 
     it 'returns group confidential issues for admin' do
-      get v3_api(base_url, admin)
+      get v3_api("#{base_url}?state=opened", admin)
 
       expect(response).to have_http_status(200)
       expect(json_response).to be_an Array
@@ -368,7 +376,7 @@ describe API::V3::Issues, api: true  do
     end
 
     it 'returns an array of issues in given milestone' do
-      get v3_api("#{base_url}?milestone=#{group_milestone.title}", user)
+      get v3_api("#{base_url}?state=opened&milestone=#{group_milestone.title}", user)
 
       expect(response).to have_http_status(200)
       expect(json_response).to be_an Array