diff --git a/packages/markers/src/browser/problem/problem-tree-model.spec.ts b/packages/markers/src/browser/problem/problem-tree-model.spec.ts
index 6271d1bc4e95c..4fe2097c62dda 100644
--- a/packages/markers/src/browser/problem/problem-tree-model.spec.ts
+++ b/packages/markers/src/browser/problem/problem-tree-model.spec.ts
@@ -125,6 +125,15 @@ describe('Problem Tree', () => {
             expect(problemTree['sortMarkers'](nodeB, nodeA)).equals(10);
         });
 
+        it('should sort markers based on owner if their severities, line numbers and columns are equal', () => {
+            const markerA = createMockMarker({ start: { line: 1, character: 10 }, end: { line: 1, character: 10 }, }, DiagnosticSeverity.Error, 'A');
+            const markerB = createMockMarker({ start: { line: 1, character: 10 }, end: { line: 1, character: 10 } }, DiagnosticSeverity.Error, 'B');
+            const nodeA = createMockMarkerNode(markerA);
+            const nodeB = createMockMarkerNode(markerB);
+            expect(problemTree['sortMarkers'](nodeA, nodeB)).equals(-1);
+            expect(problemTree['sortMarkers'](nodeB, nodeA)).equals(1);
+        });
+
         it('should not sort if markers are equal', () => {
             const markerA = createMockMarker({ start: { line: 0, character: 10 }, end: { line: 0, character: 10 } }, DiagnosticSeverity.Error);
             const markerB = createMockMarker({ start: { line: 0, character: 10 }, end: { line: 0, character: 10 } }, DiagnosticSeverity.Error);
@@ -158,19 +167,23 @@ function createMockMarkerNode(marker: Marker<Diagnostic>): MarkerNode {
  * Create a mock diagnostic marker.
  * @param range the diagnostic range.
  * @param severity the diagnostic severity.
+ * @param owner the owner of the diagnostic (optional)
  *
  * @returns a mock diagnostic marker.
  */
-function createMockMarker(range: Range, severity: DiagnosticSeverity): Readonly<Marker<Diagnostic>> {
+ function createMockMarker(range: Range, severity: DiagnosticSeverity, owner?: string): Readonly<Marker<Diagnostic>> {
     const data: Diagnostic = {
         range: range,
         severity: severity,
-        message: 'message'
+        message: 'message',
     };
+    if (!owner) {
+        owner = 'owner';
+    }
     return Object.freeze({
         uri: name,
         kind: 'marker',
-        owner: 'owner',
+        owner: owner,
         data
     });
 }
diff --git a/packages/markers/src/browser/problem/problem-tree-model.ts b/packages/markers/src/browser/problem/problem-tree-model.ts
index 55a7b1c38282b..24eb5d55bfd1d 100644
--- a/packages/markers/src/browser/problem/problem-tree-model.ts
+++ b/packages/markers/src/browser/problem/problem-tree-model.ts
@@ -65,6 +65,11 @@ export class ProblemTree extends MarkerTree<Diagnostic> {
         if (columnNumber !== 0) {
             return columnNumber;
         }
+        // Sort by owner in alphabetical order
+        const owner = ProblemUtils.ownerCompare(markerA, markerB);
+        if (owner !== 0) {
+            return owner;
+        }
         return 0;
     }
 
diff --git a/packages/markers/src/browser/problem/problem-utils.ts b/packages/markers/src/browser/problem/problem-utils.ts
index def8661895e1f..265bae8812eb5 100644
--- a/packages/markers/src/browser/problem/problem-utils.ts
+++ b/packages/markers/src/browser/problem/problem-utils.ts
@@ -45,4 +45,12 @@ export namespace ProblemUtils {
      */
     export const columnNumberCompare = (a: Marker<Diagnostic>, b: Marker<Diagnostic>): number => a.data.range.start.character - b.data.range.start.character;
 
+    /**
+     * Comparator for marker owner (source).
+     * - The order is alphabetical
+     * @param a the first marker for comparison.
+     * @param b the second marker for comparison.
+     */
+     export const ownerCompare = (a: Marker<Diagnostic>, b: Marker<Diagnostic>): number => a.owner.localeCompare(b.owner);
+
 }