diff --git a/ee/app/models/ee/merge_request.rb b/ee/app/models/ee/merge_request.rb
index ef5db8022a81bb38eaad64aefa39b027c77bb9b7..a2a2d9b06232cb16d1130f1c14a2ac12e6b8515d 100644
--- a/ee/app/models/ee/merge_request.rb
+++ b/ee/app/models/ee/merge_request.rb
@@ -755,6 +755,7 @@ def duo_code_review_progress_note
 
     def preserve_open_policy_dismissals!
       return unless merged?
+      return unless target_branch == target_project.default_branch
 
       policy_dismissals.open.find_each(&:preserve!)
     end
diff --git a/ee/spec/models/merge_request_spec.rb b/ee/spec/models/merge_request_spec.rb
index 3983e2b561f7a855fe204e21404e4ea19c33f281..d87e56270fe264df0c2858b0a8ce357568112cb8 100644
--- a/ee/spec/models/merge_request_spec.rb
+++ b/ee/spec/models/merge_request_spec.rb
@@ -3929,8 +3929,18 @@ def stub_foss_conditions_met
   end
 
   describe '#preserve_open_policy_dismissals!' do
-    let_it_be(:project) { create(:project) }
-    let_it_be(:merge_request) { create(:merge_request, :merged, source_project: project, target_project: project) }
+    let_it_be(:project) { create(:project, :repository) }
+    let_it_be(:merge_request) do
+      create(
+        :merge_request,
+        :merged,
+        source_project:
+        project,
+        target_project: project,
+        source_branch: 'feature-branch',
+        target_branch: project.default_branch
+      )
+    end
 
     subject(:preserve_open_policy_dismissals) { merge_request.preserve_open_policy_dismissals! }
 
@@ -3963,6 +3973,19 @@ def stub_foss_conditions_met
           .not_to change { open_dismissal.reload.status }
       end
     end
+
+    context 'when merge request was not merged into the default branch' do
+      let_it_be(:merge_request) do
+        create(:merge_request, :merged, source_project: project, target_project: project, target_branch: 'feature')
+      end
+
+      let_it_be(:open_dismissal) { create(:policy_dismissal, merge_request: merge_request, project: project) }
+
+      it 'returns early without processing dismissals' do
+        expect { preserve_open_policy_dismissals }
+          .not_to change { open_dismissal.reload.status }
+      end
+    end
   end
 
   describe '#all_target_branch_pipelines' do
diff --git a/ee/spec/workers/security/scan_result_policies/cleanup_merge_request_violations_worker_spec.rb b/ee/spec/workers/security/scan_result_policies/cleanup_merge_request_violations_worker_spec.rb
index 901665b7023152ff012009d21ef1b851506ee74d..b9378b66659d545016ed1c87845d3ace8946f9c2 100644
--- a/ee/spec/workers/security/scan_result_policies/cleanup_merge_request_violations_worker_spec.rb
+++ b/ee/spec/workers/security/scan_result_policies/cleanup_merge_request_violations_worker_spec.rb
@@ -3,7 +3,10 @@
 require 'spec_helper'
 
 RSpec.describe Security::ScanResultPolicies::CleanupMergeRequestViolationsWorker, '#perform', feature_category: :security_policy_management do
-  let_it_be(:merge_request) { create(:merge_request, :merged) }
+  let_it_be(:project) { create(:project, :repository) }
+  let_it_be(:merge_request) do
+    create(:merge_request, :merged, source_branch: 'feature-branch', target_branch: project.default_branch)
+  end
 
   let_it_be_with_reload(:merge_request_violation) do
     create(:scan_result_policy_violation, :running, merge_request: merge_request)