diff --git a/CHANGELOG b/CHANGELOG
index 34cf78f8f8c..f72bb670ece 100644
--- a/CHANGELOG
+++ b/CHANGELOG
@@ -128,6 +128,7 @@ v 8.6.0
   - Add main language of a project in the list of projects (Tiago Botelho)
   - Add #upcoming filter to Milestone filter (Tiago Botelho)
   - Add ability to show archived projects on dashboard, explore and group pages
+  - Remove fork link closes all merge requests opened on source project (Florent Baldino)
   - Move group activity to separate page
   - Create external users which are excluded of internal and private projects unless access was explicitly granted
   - Continue parameters are checked to ensure redirection goes to the same instance
diff --git a/app/controllers/projects_controller.rb b/app/controllers/projects_controller.rb
index 62f53664db3..8c3a74c8236 100644
--- a/app/controllers/projects_controller.rb
+++ b/app/controllers/projects_controller.rb
@@ -71,7 +71,7 @@ class ProjectsController < Projects::ApplicationController
   def remove_fork
     return access_denied! unless can?(current_user, :remove_fork_project, @project)
 
-    if @project.unlink_fork
+    if ::Projects::UnlinkForkService.new(@project, current_user).execute
       flash[:notice] = 'The fork relationship has been removed.'
     end
   end
diff --git a/app/models/merge_request.rb b/app/models/merge_request.rb
index 45c3b0a3a66..bf185cb5dd8 100644
--- a/app/models/merge_request.rb
+++ b/app/models/merge_request.rb
@@ -135,6 +135,7 @@ class MergeRequest < ActiveRecord::Base
   scope :cared, ->(user) { where('assignee_id = :user OR author_id = :user', user: user.id) }
   scope :by_milestone, ->(milestone) { where(milestone_id: milestone) }
   scope :of_projects, ->(ids) { where(target_project_id: ids) }
+  scope :from_project, ->(project) { where(source_project_id: project.id) }
   scope :merged, -> { with_state(:merged) }
   scope :closed_and_merged, -> { with_states(:closed, :merged) }
 
diff --git a/app/models/project.rb b/app/models/project.rb
index c5022fd4ffc..3e1f04b4158 100644
--- a/app/models/project.rb
+++ b/app/models/project.rb
@@ -931,16 +931,6 @@ class Project < ActiveRecord::Base
     self.builds_enabled = true
   end
 
-  def unlink_fork
-    if forked?
-      forked_from_project.lfs_objects.find_each do |lfs_object|
-        lfs_object.projects << self
-      end
-
-      forked_project_link.destroy
-    end
-  end
-
   def any_runners?(&block)
     if runners.active.any?(&block)
       return true
diff --git a/app/services/projects/unlink_fork_service.rb b/app/services/projects/unlink_fork_service.rb
new file mode 100644
index 00000000000..315c3e16292
--- /dev/null
+++ b/app/services/projects/unlink_fork_service.rb
@@ -0,0 +1,19 @@
+module Projects
+  class UnlinkForkService < BaseService
+    def execute
+      return unless @project.forked?
+
+      @project.forked_from_project.lfs_objects.find_each do |lfs_object|
+        lfs_object.projects << @project
+      end
+
+      merge_requests = @project.forked_from_project.merge_requests.opened.from_project(@project)
+
+      merge_requests.each do |mr|
+        MergeRequests::CloseService.new(@project, @current_user).execute(mr)
+      end
+
+      @project.forked_project_link.destroy
+    end
+  end
+end
diff --git a/spec/services/projects/unlink_fork_service_spec.rb b/spec/services/projects/unlink_fork_service_spec.rb
new file mode 100644
index 00000000000..23f5555d3e0
--- /dev/null
+++ b/spec/services/projects/unlink_fork_service_spec.rb
@@ -0,0 +1,32 @@
+require 'spec_helper'
+
+describe Projects::UnlinkForkService, services: true do
+  subject { Projects::UnlinkForkService.new(fork_project, user) }
+
+  let(:fork_link) { create(:forked_project_link) }
+  let(:fork_project) { fork_link.forked_to_project }
+  let(:user) { create(:user) }
+
+  context 'with opened merge request on the source project' do
+    let(:merge_request) { create(:merge_request, source_project: fork_project, target_project: fork_link.forked_from_project) }
+    let(:mr_close_service) { MergeRequests::CloseService.new(fork_project, user) }
+
+    before do
+      allow(MergeRequests::CloseService).to receive(:new).
+        with(fork_project, user).
+        and_return(mr_close_service)
+    end
+
+    it 'close all pending merge requests' do
+      expect(mr_close_service).to receive(:execute).with(merge_request)
+
+      subject.execute
+    end
+  end
+
+  it 'remove fork relation' do
+    expect(fork_project.forked_project_link).to receive(:destroy)
+
+    subject.execute
+  end
+end