diff --git a/packages/language-service/src/ts_plugin.ts b/packages/language-service/src/ts_plugin.ts
index a8da1e47a881b..fbf21b0b21a22 100644
--- a/packages/language-service/src/ts_plugin.ts
+++ b/packages/language-service/src/ts_plugin.ts
@@ -29,8 +29,16 @@ export function getExternalFiles(project: tss.server.Project): string[] {
     return [];
   }
   const ngLsHost = PROJECT_MAP.get(project);
-  ngLsHost?.getAnalyzedModules();
-  return ngLsHost?.getExternalTemplates() || [];
+  if (ngLsHost === undefined) {
+    return [];
+  }
+  ngLsHost.getAnalyzedModules();
+  return ngLsHost.getExternalTemplates().filter(fileName => {
+    // TODO(kyliau): Remove this when the following PR lands on the version of
+    // TypeScript used in this repo.
+    // https://github.com/microsoft/TypeScript/pull/41737
+    return project.fileExists(fileName);
+  });
 }
 
 export function create(info: tss.server.PluginCreateInfo): tss.LanguageService {
diff --git a/packages/language-service/test/ts_plugin_spec.ts b/packages/language-service/test/ts_plugin_spec.ts
index a57b9af930924..099146c6aedd7 100644
--- a/packages/language-service/test/ts_plugin_spec.ts
+++ b/packages/language-service/test/ts_plugin_spec.ts
@@ -21,6 +21,7 @@ const mockProject = {
     },
   },
   hasRoots: () => true,
+  fileExists: () => true,
 } as any;
 
 describe('plugin', () => {
@@ -136,6 +137,12 @@ describe('plugin', () => {
       '/app/test.ng',
     ]);
   });
+
+  it('should not return external template that does not exist', () => {
+    spyOn(mockProject, 'fileExists').and.returnValue(false);
+    const externalTemplates = getExternalFiles(mockProject);
+    expect(externalTemplates.length).toBe(0);
+  });
 });
 
 describe(`with config 'angularOnly = true`, () => {