diff --git a/app/controllers/concerns/issuable_actions.rb b/app/controllers/concerns/issuable_actions.rb
index 6fa2f75be33..94d1e8248fc 100644
--- a/app/controllers/concerns/issuable_actions.rb
+++ b/app/controllers/concerns/issuable_actions.rb
@@ -98,13 +98,12 @@ module IssuableActions
     render json: { notice: "#{quantity} #{resource_name.pluralize(quantity)} updated" }
   end
 
-  # rubocop: disable CodeReuse/ActiveRecord
+  # rubocop:disable CodeReuse/ActiveRecord
   def discussions
-    notes = issuable.discussion_notes
-      .inc_relations_for_view
-      .with_notes_filter(notes_filter)
-      .includes(:noteable)
-      .fresh
+    notes = NotesFinder.new(project, current_user, finder_params_for_issuable).execute
+                .inc_relations_for_view
+                .includes(:noteable)
+                .fresh
 
     if notes_filter != UserPreference::NOTES_FILTERS[:only_comments]
       notes = ResourceEvents::MergeIntoNotesService.new(issuable, current_user).execute(notes)
@@ -117,7 +116,7 @@ module IssuableActions
 
     render json: discussion_serializer.represent(discussions, context: self)
   end
-  # rubocop: enable CodeReuse/ActiveRecord
+  # rubocop:enable CodeReuse/ActiveRecord
 
   private
 
@@ -222,4 +221,13 @@ module IssuableActions
   def parent
     @project || @group # rubocop:disable Gitlab/ModuleWithInstanceVariables
   end
+
+  # rubocop:disable Gitlab/ModuleWithInstanceVariables
+  def finder_params_for_issuable
+    {
+        target: @issuable,
+        notes_filter: notes_filter
+    }
+  end
+  # rubocop:enable Gitlab/ModuleWithInstanceVariables
 end
diff --git a/app/finders/notes_finder.rb b/app/finders/notes_finder.rb
index 8f610d7dddb..c25600221d7 100644
--- a/app/finders/notes_finder.rb
+++ b/app/finders/notes_finder.rb
@@ -3,6 +3,8 @@
 class NotesFinder
   FETCH_OVERLAP = 5.seconds
 
+  attr_reader :target_type
+
   # Used to filter Notes
   # When used with target_type and target_id this returns notes specifically for the controller
   #
@@ -10,6 +12,7 @@ class NotesFinder
   #   current_user - which user check authorizations with
   #   project - which project to look for notes on
   #   params:
+  #     target: noteable
   #     target_type: string
   #     target_id: integer
   #     last_fetched_at: time
@@ -18,7 +21,8 @@ class NotesFinder
   def initialize(project, current_user, params = {})
     @project = project
     @current_user = current_user
-    @params = params
+    @params = params.dup
+    @target_type = @params[:target_type]
   end
 
   def execute
@@ -32,7 +36,27 @@ class NotesFinder
   def target
     return @target if defined?(@target)
 
-    target_type = @params[:target_type]
+    if target_given?
+      use_explicit_target
+    else
+      find_target_by_type_and_ids
+    end
+  end
+
+  private
+
+  def target_given?
+    @params.key?(:target)
+  end
+
+  def use_explicit_target
+    @target = @params[:target]
+    @target_type = @target.class.name.underscore
+
+    @target
+  end
+
+  def find_target_by_type_and_ids
     target_id   = @params[:target_id]
     target_iid  = @params[:target_iid]
 
@@ -45,13 +69,11 @@ class NotesFinder
           @project.commit(target_id)
         end
       else
-        noteables_for_type_by_id(target_type, target_id, target_iid)
+        noteable_for_type_by_id(target_type, target_id, target_iid)
       end
   end
 
-  private
-
-  def noteables_for_type_by_id(type, id, iid)
+  def noteable_for_type_by_id(type, id, iid)
     query = if id
               { id: id }
             else
@@ -77,10 +99,6 @@ class NotesFinder
     search(notes)
   end
 
-  def target_type
-    @params[:target_type]
-  end
-
   # rubocop: disable CodeReuse/ActiveRecord
   def notes_of_any_type
     types = %w(commit issue merge_request snippet)
diff --git a/spec/controllers/concerns/issuable_actions_spec.rb b/spec/controllers/concerns/issuable_actions_spec.rb
new file mode 100644
index 00000000000..3281fd4a2ef
--- /dev/null
+++ b/spec/controllers/concerns/issuable_actions_spec.rb
@@ -0,0 +1,69 @@
+# frozen_string_literal: true
+
+require 'spec_helper'
+
+describe IssuableActions do
+  let(:project) { double('project') }
+  let(:user) { double('user') }
+  let(:issuable) { double('issuable') }
+  let(:finder_params_for_issuable) { {} }
+  let(:notes_result) { double('notes_result') }
+  let(:discussion_serializer) { double('discussion_serializer') }
+
+  let(:controller) do
+    klass = Class.new do
+      attr_reader :current_user, :project, :issuable
+
+      def self.before_action(action, params = nil)
+      end
+
+      include IssuableActions
+
+      def initialize(issuable, project, user, finder_params)
+        @issuable = issuable
+        @project = project
+        @current_user = user
+        @finder_params = finder_params
+      end
+
+      def finder_params_for_issuable
+        @finder_params
+      end
+
+      def params
+        {
+          notes_filter: 1
+        }
+      end
+
+      def prepare_notes_for_rendering(notes)
+        []
+      end
+
+      def render(options)
+      end
+    end
+
+    klass.new(issuable, project, user, finder_params_for_issuable)
+  end
+
+  describe '#discussions' do
+    before do
+      allow(user).to receive(:set_notes_filter)
+      allow(user).to receive(:user_preference)
+      allow(discussion_serializer).to receive(:represent)
+    end
+
+    it 'instantiates and calls NotesFinder as expected' do
+      expect(Discussion).to receive(:build_collection).and_return([])
+      expect(DiscussionSerializer).to receive(:new).and_return(discussion_serializer)
+      expect(NotesFinder).to receive(:new).with(project, user, finder_params_for_issuable).and_call_original
+
+      expect_any_instance_of(NotesFinder).to receive(:execute).and_return(notes_result)
+
+      expect(notes_result).to receive_messages(inc_relations_for_view: notes_result, includes: notes_result, fresh: notes_result)
+
+      controller.discussions
+    end
+  end
+end
diff --git a/spec/controllers/projects/issues_controller_spec.rb b/spec/controllers/projects/issues_controller_spec.rb
index 32d14dce936..0f885d776e1 100644
--- a/spec/controllers/projects/issues_controller_spec.rb
+++ b/spec/controllers/projects/issues_controller_spec.rb
@@ -1260,6 +1260,28 @@ describe Projects::IssuesController do
         sign_in(user)
       end
 
+      context do
+        it_behaves_like 'discussions provider' do
+          let!(:author) { create(:user) }
+          let!(:project) { create(:project) }
+
+          let!(:issue) { create(:issue, project: project, author: user) }
+
+          let!(:note_on_issue1) { create(:discussion_note_on_issue, noteable: issue, project: issue.project, author: create(:user)) }
+          let!(:note_on_issue2) { create(:discussion_note_on_issue, noteable: issue, project: issue.project, author: create(:user)) }
+
+          let(:requested_iid) { issue.iid }
+          let(:expected_discussion_count) { 3 }
+          let(:expected_discussion_ids) do
+            [
+              issue.notes.first.discussion_id,
+              note_on_issue1.discussion_id,
+              note_on_issue2.discussion_id
+            ]
+          end
+        end
+      end
+
       it 'returns discussion json' do
         get :discussions, params: { namespace_id: project.namespace, project_id: project, id: issue.iid }
 
diff --git a/spec/controllers/projects/merge_requests_controller_spec.rb b/spec/controllers/projects/merge_requests_controller_spec.rb
index fa71d9b61b1..9aa5f1ade8d 100644
--- a/spec/controllers/projects/merge_requests_controller_spec.rb
+++ b/spec/controllers/projects/merge_requests_controller_spec.rb
@@ -1120,6 +1120,22 @@ describe Projects::MergeRequestsController do
         end
       end
     end
+
+    context do
+      it_behaves_like 'discussions provider' do
+        let!(:author) { create(:user) }
+        let!(:project) { create(:project) }
+
+        let!(:merge_request) { create(:merge_request, source_project: project) }
+
+        let!(:mr_note1) { create(:discussion_note_on_merge_request, noteable: merge_request, project: project) }
+        let!(:mr_note2) { create(:discussion_note_on_merge_request, noteable: merge_request, project: project) }
+
+        let(:requested_iid) { merge_request.iid }
+        let(:expected_discussion_count) { 2 }
+        let(:expected_discussion_ids) { [mr_note1.discussion_id, mr_note2.discussion_id] }
+      end
+    end
   end
 
   describe 'GET edit' do
diff --git a/spec/finders/notes_finder_spec.rb b/spec/finders/notes_finder_spec.rb
index 87bde4ca2f6..677fde0d8ce 100644
--- a/spec/finders/notes_finder_spec.rb
+++ b/spec/finders/notes_finder_spec.rb
@@ -118,16 +118,11 @@ describe NotesFinder do
 
     context 'for target' do
       let(:project) { create(:project, :repository) }
-      let(:note1) { create :note_on_commit, project: project }
-      let(:note2) { create :note_on_commit, project: project }
+      let!(:note1) { create :note_on_commit, project: project }
+      let!(:note2) { create :note_on_commit, project: project }
       let(:commit) { note1.noteable }
       let(:params) { { target_id: commit.id, target_type: 'commit', last_fetched_at: 1.hour.ago.to_i } }
 
-      before do
-        note1
-        note2
-      end
-
       it 'finds all notes' do
         notes = described_class.new(project, user, params).execute
         expect(notes.size).to eq(2)
@@ -194,6 +189,28 @@ describe NotesFinder do
         end
       end
     end
+
+    context 'for explicit target' do
+      let(:project) { create(:project, :repository) }
+      let!(:note1) { create :note_on_commit, project: project, created_at: 1.day.ago, updated_at: 2.hours.ago }
+      let!(:note2) { create :note_on_commit, project: project }
+      let(:commit) { note1.noteable }
+      let(:params) { { target: commit } }
+
+      it 'returns the expected notes' do
+        expect(described_class.new(project, user, params).execute).to eq([note1, note2])
+      end
+
+      it 'returns the expected notes when last_fetched_at is given' do
+        params = { target: commit, last_fetched_at: 1.hour.ago.to_i }
+        expect(described_class.new(project, user, params).execute).to eq([note2])
+      end
+
+      it 'fails when nil is provided' do
+        params = { target: nil }
+        expect { described_class.new(project, user, params).execute }.to raise_error(RuntimeError)
+      end
+    end
   end
 
   describe '.search' do
diff --git a/spec/fixtures/api/schemas/entities/discussion.json b/spec/fixtures/api/schemas/entities/discussion.json
new file mode 100644
index 00000000000..bcc1db79e83
--- /dev/null
+++ b/spec/fixtures/api/schemas/entities/discussion.json
@@ -0,0 +1,67 @@
+{
+  "type": "object",
+  "required" : [
+    "id",
+    "notes",
+    "individual_note"
+  ],
+  "properties" : {
+    "id": { "type": "string" },
+    "individual_note": { "type": "boolean" },
+    "notes": {
+      "type": "array",
+      "items": {
+        "type": "object",
+        "properties" : {
+          "id": { "type": "string" },
+          "type": { "type": ["string", "null"] },
+          "body": { "type": "string" },
+          "attachment": { "type": ["string", "null"]},
+          "award_emoji": { "type": "array" },
+          "author": {
+            "type": "object",
+            "properties": {
+              "name": { "type": "string" },
+              "username": { "type": "string" },
+              "id": { "type": "integer" },
+              "state": { "type": "string" },
+              "avatar_url": { "type": "uri" },
+              "web_url": { "type": "uri" },
+              "status_tooltip_html": { "type": ["string", "null"] },
+              "path": { "type": "string" }
+            },
+            "additionalProperties": false
+          },
+          "created_at": { "type": "date" },
+          "updated_at": { "type": "date" },
+          "system": { "type": "boolean" },
+          "noteable_id": { "type": "integer" },
+          "noteable_iid": { "type": "integer" },
+          "noteable_type": { "type": "string" },
+          "resolved": { "type": "boolean" },
+          "resolvable": { "type": "boolean" },
+          "resolved_by": { "type": ["string", "null"] },
+          "note": { "type": "string" },
+          "note_html": { "type": "string"  },
+          "current_user": { "type": "object" },
+          "suggestions": { "type": "array" },
+          "discussion_id": { "type": "string" },
+          "emoji_awardable": { "type": "boolean" },
+          "report_abuse_path": { "type": "string" },
+          "noteable_note_url": { "type": "string" },
+          "resolve_path": { "type": "string" },
+          "resolve_with_issue_path": { "type": "string" },
+          "cached_markdown_version": { "type": "integer" },
+          "human_access": { "type": ["string", "null"] },
+          "toggle_award_path": { "type": "string" },
+          "path": { "type": "string" }
+        },
+        "required": [
+          "id", "attachment", "author", "created_at", "updated_at",
+          "system", "noteable_id", "noteable_type"
+        ],
+        "additionalProperties": false
+      }
+    }
+  }
+}
diff --git a/spec/fixtures/api/schemas/entities/discussions.json b/spec/fixtures/api/schemas/entities/discussions.json
new file mode 100644
index 00000000000..5a837429776
--- /dev/null
+++ b/spec/fixtures/api/schemas/entities/discussions.json
@@ -0,0 +1,4 @@
+{
+  "type": "array",
+  "items": { "$ref": "discussion.json" }
+}
diff --git a/spec/support/shared_examples/discussions_provider_shared_examples.rb b/spec/support/shared_examples/discussions_provider_shared_examples.rb
new file mode 100644
index 00000000000..77cf1ac3f51
--- /dev/null
+++ b/spec/support/shared_examples/discussions_provider_shared_examples.rb
@@ -0,0 +1,15 @@
+# frozen_string_literal: true
+
+require 'spec_helper'
+
+shared_examples 'discussions provider' do
+  it 'returns the expected discussions' do
+    get :discussions, params: { namespace_id: project.namespace, project_id: project, id: requested_iid }
+
+    expect(response).to have_gitlab_http_status(200)
+    expect(response).to match_response_schema('entities/discussions')
+
+    expect(json_response.size).to eq(expected_discussion_count)
+    expect(json_response.pluck('id')).to eq(expected_discussion_ids)
+  end
+end