diff --git a/packages/compiler-cli/src/ngtsc/typecheck/extended/test/checks/nullish_coalescing_not_nullable/BUILD.bazel b/packages/compiler-cli/src/ngtsc/typecheck/extended/test/checks/nullish_coalescing_not_nullable/BUILD.bazel
new file mode 100644
index 00000000000..30f1f8f4789
--- /dev/null
+++ b/packages/compiler-cli/src/ngtsc/typecheck/extended/test/checks/nullish_coalescing_not_nullable/BUILD.bazel
@@ -0,0 +1,26 @@
+load("//tools:defaults.bzl", "jasmine_node_test", "ts_library")
+
+ts_library(
+    name = "test_lib",
+    testonly = True,
+    srcs = ["spec.ts"],
+    deps = [
+        "//packages/compiler",
+        "//packages/compiler-cli/src/ngtsc/diagnostics",
+        "//packages/compiler-cli/src/ngtsc/file_system",
+        "//packages/compiler-cli/src/ngtsc/file_system/testing",
+        "//packages/compiler-cli/src/ngtsc/testing",
+        "//packages/compiler-cli/src/ngtsc/typecheck/extended",
+        "//packages/compiler-cli/src/ngtsc/typecheck/extended/checks/nullish_coalescing_not_nullable",
+        "//packages/compiler-cli/src/ngtsc/typecheck/testing",
+        "@npm//typescript",
+    ],
+)
+
+jasmine_node_test(
+    name = "test",
+    bootstrap = ["//tools/testing:node_no_angular_es5"],
+    deps = [
+        ":test_lib",
+    ],
+)
diff --git a/packages/compiler-cli/src/ngtsc/typecheck/extended/test/checks/nullish_coalescing_not_nullable/spec.ts b/packages/compiler-cli/src/ngtsc/typecheck/extended/test/checks/nullish_coalescing_not_nullable/spec.ts
new file mode 100644
index 00000000000..3bed38765ad
--- /dev/null
+++ b/packages/compiler-cli/src/ngtsc/typecheck/extended/test/checks/nullish_coalescing_not_nullable/spec.ts
@@ -0,0 +1,75 @@
+/**
+ * @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 * as ts from 'typescript';
+
+import {ErrorCode, ngErrorCode} from '../../../../../diagnostics';
+import {absoluteFrom, getSourceFileOrError} from '../../../../../file_system';
+import {runInEachFileSystem} from '../../../../../file_system/testing';
+import {getSourceCodeForDiagnostic} from '../../../../../testing';
+import {getClass, setup} from '../../../../testing';
+import {NullishCoalescingNotNullableCheck} from '../../../checks/nullish_coalescing_not_nullable';
+import {ExtendedTemplateCheckerImpl} from '../../../src/extended_template_checker';
+
+runInEachFileSystem(() => {
+  describe('NullishCoalescingNotNullableCheck', () => {
+    it('should produce nullish coalescing warning', () => {
+      const fileName = absoluteFrom('/main.ts');
+      const {program, templateTypeChecker} = setup([{
+        fileName,
+        templates: {
+          'TestCmp': `{{ var1 ?? 'foo' }}`,
+        },
+        source: 'export class TestCmp { var1: string = "text"; }'
+      }]);
+      const sf = getSourceFileOrError(program, fileName);
+      const component = getClass(sf, 'TestCmp');
+      const extendedTemplateChecker = new ExtendedTemplateCheckerImpl(
+          templateTypeChecker, program.getTypeChecker(), [new NullishCoalescingNotNullableCheck()]);
+      const diags = extendedTemplateChecker.getDiagnosticsForComponent(component);
+      expect(diags.length).toBe(1);
+      expect(diags[0].category).toBe(ts.DiagnosticCategory.Warning);
+      expect(diags[0].code).toBe(ngErrorCode(ErrorCode.NULLISH_COALESCING_NOT_NULLABLE));
+      expect(getSourceCodeForDiagnostic(diags[0])).toBe(`var1 ?? 'foo'`);
+    });
+
+    it('should not produce nullish coalescing warning for a nullable type', () => {
+      const fileName = absoluteFrom('/main.ts');
+      const {program, templateTypeChecker} = setup([{
+        fileName,
+        templates: {
+          'TestCmp': `{{ var1 ?? 'foo' }}`,
+        },
+        source: 'export class TestCmp { var1: string | null = "text"; }'
+      }]);
+      const sf = getSourceFileOrError(program, fileName);
+      const component = getClass(sf, 'TestCmp');
+      const extendedTemplateChecker = new ExtendedTemplateCheckerImpl(
+          templateTypeChecker, program.getTypeChecker(), [new NullishCoalescingNotNullableCheck()]);
+      const diags = extendedTemplateChecker.getDiagnosticsForComponent(component);
+      expect(diags.length).toBe(0);
+    });
+
+    it('should not produce nullish coalescing warning for a type that includes undefined', () => {
+      const fileName = absoluteFrom('/main.ts');
+      const {program, templateTypeChecker} = setup([{
+        fileName,
+        templates: {
+          'TestCmp': `{{ var1 ?? 'foo' }}`,
+        },
+        source: 'export class TestCmp { var1: string | undefined = "text"; }'
+      }]);
+      const sf = getSourceFileOrError(program, fileName);
+      const component = getClass(sf, 'TestCmp');
+      const extendedTemplateChecker = new ExtendedTemplateCheckerImpl(
+          templateTypeChecker, program.getTypeChecker(), [new NullishCoalescingNotNullableCheck()]);
+      const diags = extendedTemplateChecker.getDiagnosticsForComponent(component);
+      expect(diags.length).toBe(0);
+    });
+  });
+});
diff --git a/packages/compiler-cli/test/ngtsc/extended_template_diagnostics_spec.ts b/packages/compiler-cli/test/ngtsc/extended_template_diagnostics_spec.ts
index 34681759bdc..e00e6fb3371 100644
--- a/packages/compiler-cli/test/ngtsc/extended_template_diagnostics_spec.ts
+++ b/packages/compiler-cli/test/ngtsc/extended_template_diagnostics_spec.ts
@@ -103,5 +103,43 @@ runInEachFileSystem(() => {
              .toMatch(
                  /Error: The '_extendedTemplateDiagnostics' option requires 'strictTemplates' to also be enabled./);
        });
+
+    it(`should produce nullish coalescing not nullable warning`, () => {
+      env.write('test.ts', `
+              import {Component} from '@angular/core';
+              @Component({
+                selector: 'test',
+                template: '{{ bar ?? "foo" }}',
+              })
+              export class TestCmp { 
+                bar: string = "text"; 
+              }
+            `);
+
+      const diags = env.driveDiagnostics();
+      expect(diags.length).toBe(1);
+      expect(diags[0].category).toBe(ts.DiagnosticCategory.Warning);
+      expect(diags[0].code).toBe(ngErrorCode(ErrorCode.NULLISH_COALESCING_NOT_NULLABLE));
+      expect(getSourceCodeForDiagnostic(diags[0])).toBe('bar ?? "foo"');
+    });
+
+    it(`should not produce nullish coalescing not nullable warning with strictNullChecks disabled`,
+       () => {
+         env.tsconfig(
+             {_extendedTemplateDiagnostics: true, strictTemplates: true, strictNullChecks: false});
+         env.write('test.ts', `
+              import {Component} from '@angular/core';
+              @Component({
+                selector: 'test',
+                template: '{{ bar ?? "foo" }}',
+              })
+              export class TestCmp { 
+                bar: string = undefined; 
+              }
+            `);
+
+         const diags = env.driveDiagnostics();
+         expect(diags.length).toBe(0);
+       });
   });
 });