diff --git a/src/cdk/testing/component-harness.ts b/src/cdk/testing/component-harness.ts
index 865b47c037cc..455fd5fdd54b 100644
--- a/src/cdk/testing/component-harness.ts
+++ b/src/cdk/testing/component-harness.ts
@@ -520,9 +520,25 @@ export class HarnessPredicate<T extends ComponentHarness> {
 
   /** Gets the selector used to find candidate elements. */
   getSelector() {
-    return this._ancestor.split(',')
-        .map(part => `${part.trim()} ${this.harnessType.hostSelector}`.trim())
-        .join(',');
+    // We don't have to go through the extra trouble if there are no ancestors.
+    if (!this._ancestor) {
+      return (this.harnessType.hostSelector || '').trim();
+    }
+
+    const [ancestors, ancestorPlaceholders] = _splitAndEscapeSelector(this._ancestor);
+    const [selectors, selectorPlaceholders] =
+      _splitAndEscapeSelector(this.harnessType.hostSelector || '');
+    const result: string[] = [];
+
+    // We have to add the ancestor to each part of the host compound selector, otherwise we can get
+    // incorrect results. E.g. `.ancestor .a, .ancestor .b` vs `.ancestor .a, .b`.
+    ancestors.forEach(escapedAncestor => {
+      const ancestor = _restoreSelector(escapedAncestor, ancestorPlaceholders);
+      return selectors.forEach(escapedSelector =>
+        result.push(`${ancestor} ${_restoreSelector(escapedSelector, selectorPlaceholders)}`));
+    });
+
+    return result.join(', ');
   }
 
   /** Adds base options common to all harness types. */
@@ -560,3 +576,34 @@ function _valueAsString(value: unknown) {
     return '{...}';
   }
 }
+
+/**
+ * Splits up a compound selector into its parts and escapes any quoted content. The quoted content
+ * has to be escaped, because it can contain commas which will throw throw us off when trying to
+ * split it.
+ * @param selector Selector to be split.
+ * @returns The escaped string where any quoted content is replaced with a placeholder. E.g.
+ * `[foo="bar"]` turns into `[foo=__cdkPlaceholder-0__]`. Use `_restoreSelector` to restore
+ * the placeholders.
+ */
+function _splitAndEscapeSelector(selector: string): [parts: string[], placeholders: string[]] {
+  const placeholders: string[] = [];
+
+  // Note that the regex doesn't account for nested quotes so something like `"ab'cd'e"` will be
+  // considered as two blocks. It's a bit of an edge case, but if we find that it's a problem,
+  // we can make it a bit smarter using a loop. Use this for now since it's more readable and
+  // compact. More complete implementation:
+  // https://github.com/angular/angular/blob/bd34bc9e89f18a/packages/compiler/src/shadow_css.ts#L655
+  const result = selector.replace(/(["'][^["']*["'])/g, (_, keep) => {
+    const replaceBy = `__cdkPlaceholder-${placeholders.length}__`;
+    placeholders.push(keep);
+    return replaceBy;
+  });
+
+  return [result.split(',').map(part => part.trim()), placeholders];
+}
+
+/** Restores a selector whose content was escaped in `_splitAndEscapeSelector`. */
+function _restoreSelector(selector: string, placeholders: string[]): string {
+  return selector.replace(/__cdkPlaceholder-(\d+)__/g, (_, index) => placeholders[+index]);
+}
diff --git a/src/cdk/testing/tests/cross-environment.spec.ts b/src/cdk/testing/tests/cross-environment.spec.ts
index e48e23f4c113..5d10c7bf9cc9 100644
--- a/src/cdk/testing/tests/cross-environment.spec.ts
+++ b/src/cdk/testing/tests/cross-environment.spec.ts
@@ -246,6 +246,15 @@ export function crossEnvironmentSpecs(
       const subcomps = await harness.directAncestorSelectorSubcomponent();
       expect(subcomps.length).toBe(2);
     });
+
+    it('should handle a compound selector with an ancestor', async () => {
+      const elements = await harness.compoundSelectorWithAncestor();
+
+      expect(await parallel(() => elements.map(element => element.getText()))).toEqual([
+        'Div inside parent',
+        'Span inside parent'
+      ]);
+    });
   });
 
   describe('HarnessPredicate', () => {
diff --git a/src/cdk/testing/tests/harnesses/compound-selector-harness.ts b/src/cdk/testing/tests/harnesses/compound-selector-harness.ts
new file mode 100644
index 000000000000..c864c3732852
--- /dev/null
+++ b/src/cdk/testing/tests/harnesses/compound-selector-harness.ts
@@ -0,0 +1,21 @@
+/**
+ * @license
+ * Copyright Google LLC All Rights Reserved.
+ *
+ * Use of this source code is governed by an MIT-style license that can be
+ * found in the LICENSE file at https://angular.io/license
+ */
+
+import {ComponentHarness, HarnessPredicate} from '../../component-harness';
+
+export class CompoundSelectorHarness extends ComponentHarness {
+  static readonly hostSelector = '.some-div, .some-span';
+
+  static with(options = {}) {
+    return new HarnessPredicate(CompoundSelectorHarness, options);
+  }
+
+  async getText(): Promise<string> {
+    return (await this.host()).text();
+  }
+}
diff --git a/src/cdk/testing/tests/harnesses/main-component-harness.ts b/src/cdk/testing/tests/harnesses/main-component-harness.ts
index a47d060f396e..7be61c6e1549 100644
--- a/src/cdk/testing/tests/harnesses/main-component-harness.ts
+++ b/src/cdk/testing/tests/harnesses/main-component-harness.ts
@@ -8,6 +8,7 @@
 
 import {ComponentHarness} from '../../component-harness';
 import {TestElement, TestKey} from '../../test-element';
+import {CompoundSelectorHarness} from './compound-selector-harness';
 import {SubComponentHarness, SubComponentSpecialHarness} from './sub-component-harness';
 
 export class WrongComponentHarness extends ComponentHarness {
@@ -81,6 +82,8 @@ export class MainComponentHarness extends ComponentHarness {
       this.locatorForAll(SubComponentHarness.with({ancestor: '.other, .subcomponents'}));
   readonly directAncestorSelectorSubcomponent =
       this.locatorForAll(SubComponentHarness.with({ancestor: '.other >'}));
+  readonly compoundSelectorWithAncestor =
+      this.locatorForAll(CompoundSelectorHarness.with({ancestor: '.parent'}));
 
   readonly subcomponentHarnessesAndElements =
       this.locatorForAll('#counter', SubComponentHarness);
diff --git a/src/cdk/testing/tests/test-main-component.html b/src/cdk/testing/tests/test-main-component.html
index 67a676f32ec1..d95acf798b43 100644
--- a/src/cdk/testing/tests/test-main-component.html
+++ b/src/cdk/testing/tests/test-main-component.html
@@ -57,6 +57,12 @@ <h1 style="height: 100px; width: 200px;">Main Component</h1>
   <test-sub title="other 1"></test-sub>
   <test-sub title="other 2"></test-sub>
 </div>
+<div class="parent">
+  <div class="some-div">Div inside parent</div>
+  <div class="some-span">Span inside parent</div>
+</div>
+<div class="some-div">Div outside parent</div>
+<div class="some-span">Span outside parent</div>
 <div class="task-state-tests">
   <button (click)="runTaskOutsideZone()" id="task-state-test-trigger">
     Run task outside zone