diff --git a/app/models/user.rb b/app/models/user.rb
index 7b6857a0d347a3b386d680775805baa1e8c019a3..ce56b39b1c8aba391a1cc3e78bf9004c8791d97a 100644
--- a/app/models/user.rb
+++ b/app/models/user.rb
@@ -1046,11 +1046,6 @@ class User < ActiveRecord::Base
     end
   end
 
-  def update_cache_counts
-    assigned_open_merge_requests_count(force: true)
-    assigned_open_issues_count(force: true)
-  end
-
   def update_todos_count_cache
     todos_done_count(force: true)
     todos_pending_count(force: true)
diff --git a/app/services/issuable/destroy_service.rb b/app/services/issuable/destroy_service.rb
index 7197a426a726f76542264b2e0e32a044a74e87b2..0b1a33518c6e88499168b1c9baa78fe4e63e4016 100644
--- a/app/services/issuable/destroy_service.rb
+++ b/app/services/issuable/destroy_service.rb
@@ -4,6 +4,7 @@ module Issuable
       TodoService.new.destroy_target(issuable) do |issuable|
         if issuable.destroy
           issuable.update_project_counter_caches
+          issuable.assignees.each(&:invalidate_cache_counts)
         end
       end
     end
diff --git a/changelogs/unreleased/ui-mr-counter-cache.yml b/changelogs/unreleased/ui-mr-counter-cache.yml
new file mode 100644
index 0000000000000000000000000000000000000000..5e241bfe93f7985dee2b9f82fa7d9111de5212cc
--- /dev/null
+++ b/changelogs/unreleased/ui-mr-counter-cache.yml
@@ -0,0 +1,5 @@
+---
+title: Deleting a MR you are assigned to should decrements counter
+merge_request: 17951
+author: m b
+type: fixed
diff --git a/spec/services/issuable/destroy_service_spec.rb b/spec/services/issuable/destroy_service_spec.rb
index 0a3647a814f714f57a659a0f23d8c0aac8cdd062..8ccbba7fa58195bfc8e7036259c4cfb114db91c1 100644
--- a/spec/services/issuable/destroy_service_spec.rb
+++ b/spec/services/issuable/destroy_service_spec.rb
@@ -8,7 +8,7 @@ describe Issuable::DestroyService do
 
   describe '#execute' do
     context 'when issuable is an issue' do
-      let!(:issue) { create(:issue, project: project, author: user) }
+      let!(:issue) { create(:issue, project: project, author: user, assignees: [user]) }
 
       it 'destroys the issue' do
         expect { service.execute(issue) }.to change { project.issues.count }.by(-1)
@@ -26,10 +26,15 @@ describe Issuable::DestroyService do
         expect { service.execute(issue) }
           .to change { user.todos_pending_count }.from(1).to(0)
       end
+
+      it 'invalidates the issues count cache for the assignees' do
+        expect_any_instance_of(User).to receive(:invalidate_cache_counts).once
+        service.execute(issue)
+      end
     end
 
     context 'when issuable is a merge request' do
-      let!(:merge_request) { create(:merge_request, target_project: project, source_project: project, author: user) }
+      let!(:merge_request) { create(:merge_request, target_project: project, source_project: project, author: user, assignee: user) }
 
       it 'destroys the merge request' do
         expect { service.execute(merge_request) }.to change { project.merge_requests.count }.by(-1)
@@ -41,6 +46,11 @@ describe Issuable::DestroyService do
         service.execute(merge_request)
       end
 
+      it 'invalidates the merge request caches for the MR assignee' do
+        expect_any_instance_of(User).to receive(:invalidate_cache_counts).once
+        service.execute(merge_request)
+      end
+
       it 'updates the todo caches for users with todos on the merge request' do
         create(:todo, target: merge_request, user: user, author: user, project: project)