diff --git a/app/services/delete_merged_branches_service.rb b/app/services/delete_merged_branches_service.rb
index 5c9e2a16c71..ff11bd59d29 100644
--- a/app/services/delete_merged_branches_service.rb
+++ b/app/services/delete_merged_branches_service.rb
@@ -11,7 +11,7 @@ class DeleteMergedBranchesService < BaseService
     # Prevent deletion of branches relevant to open merge requests
     branches -= merge_request_branch_names
     # Prevent deletion of protected branches
-    branches -= project.protected_branches.pluck(:name)
+    branches = branches.reject { |branch| project.protected_for?(branch) }
 
     branches.each do |branch|
       DeleteBranchService.new(project, current_user).execute(branch)
diff --git a/changelogs/unreleased/tc-fix-wildcard-protected-delete-merged.yml b/changelogs/unreleased/tc-fix-wildcard-protected-delete-merged.yml
new file mode 100644
index 00000000000..9ca5f81cf79
--- /dev/null
+++ b/changelogs/unreleased/tc-fix-wildcard-protected-delete-merged.yml
@@ -0,0 +1,4 @@
+---
+title: Make Delete Merged Branches handle wildcard protected branches correctly
+merge_request: 13251
+author:
diff --git a/spec/services/delete_merged_branches_service_spec.rb b/spec/services/delete_merged_branches_service_spec.rb
index 4b872d667cf..03c682ae0d7 100644
--- a/spec/services/delete_merged_branches_service_spec.rb
+++ b/spec/services/delete_merged_branches_service_spec.rb
@@ -32,6 +32,14 @@ describe DeleteMergedBranchesService do
       expect(project.repository.branch_names).to include('improve/awesome')
     end
 
+    it 'keeps wildcard protected branches' do
+      create(:protected_branch, project: project, name: 'improve/*')
+
+      service.execute
+
+      expect(project.repository.branch_names).to include('improve/awesome')
+    end
+
     context 'user without rights' do
       let(:user) { create(:user) }