diff --git a/CHANGELOG.md b/CHANGELOG.md
index 070258d7a0b3..ae495aaca133 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -16,6 +16,7 @@
 - `[@jest/core]` Support `--outputFile` option for [`--listTests`](https://jestjs.io/docs/cli#--listtests) ([#14980](https://github.com/jestjs/jest/pull/14980))
 - `[@jest/core, @jest/test-sequencer]` [**BREAKING**] Exposes `globalConfig` & `contexts` to `TestSequencer` ([#14535](https://github.com/jestjs/jest/pull/14535), & [#14543](https://github.com/jestjs/jest/pull/14543))
 - `[@jest/environment]` [**BREAKING**] Remove deprecated `jest.genMockFromModule()` ([#15042](https://github.com/jestjs/jest/pull/15042))
+- `[@jest/environment]` [**BREAKING**] Remove unnecessary defensive code ([#15045](https://github.com/jestjs/jest/pull/15045))
 - `[jest-environment-jsdom]` [**BREAKING**] Upgrade JSDOM to v22 ([#13825](https://github.com/jestjs/jest/pull/13825))
 - `[@jest/environment-jsdom-abstract]` Introduce new package which abstracts over the `jsdom` environment, allowing usage of custom versions of JSDOM ([#14717](https://github.com/jestjs/jest/pull/14717))
 - `[jest-environment-node]` Update jest environment with dispose symbols `Symbol` ([#14888](https://github.com/jestjs/jest/pull/14888) & [#14909](https://github.com/jestjs/jest/pull/14909))
diff --git a/e2e/__tests__/testEnvironment.test.ts b/e2e/__tests__/testEnvironment.test.ts
index 29b8e2e875c7..3f4a31a91c11 100644
--- a/e2e/__tests__/testEnvironment.test.ts
+++ b/e2e/__tests__/testEnvironment.test.ts
@@ -5,18 +5,9 @@
  * LICENSE file in the root directory of this source tree.
  */
 
-import {tmpdir} from 'os';
-import * as path from 'path';
-import slash = require('slash');
-import {cleanup, createEmptyPackage, writeFiles} from '../Utils';
-import runJest, {json as runWithJson} from '../runJest';
+import {json as runWithJson} from '../runJest';
 import * as testFixturePackage from '../test-environment/package.json';
 
-const DIR = path.resolve(tmpdir(), 'test-env-no-mocked');
-
-beforeEach(() => cleanup(DIR));
-afterAll(() => cleanup(DIR));
-
 it('respects testEnvironment docblock', () => {
   expect(testFixturePackage.jest.testEnvironment).toBe('node');
 
@@ -25,40 +16,3 @@ it('respects testEnvironment docblock', () => {
   expect(result.success).toBe(true);
   expect(result.numTotalTests).toBe(4);
 });
-
-it('handles missing `mocked` property', () => {
-  createEmptyPackage(DIR);
-  writeFiles(DIR, {
-    'env.js': `
-      const Node = require('${slash(
-        require.resolve('jest-environment-node'),
-      )}').default;
-
-      module.exports = class Thing extends Node {
-        constructor(...args) {
-          super(...args);
-
-          this.moduleMocker.mocked = undefined;
-        }
-      };
-    `,
-    'test.js': `
-      /**
-       * @jest-environment ./env.js
-       */
-
-      jest.mocked();
-
-      test('halla', () => {
-        expect(globalThis.thing).toBe('nope');
-      });
-    `,
-  });
-
-  const {exitCode, stderr} = runJest(DIR);
-
-  expect(exitCode).toBe(1);
-  expect(stderr).toContain(
-    'Your test environment does not support `mocked`, please update it.',
-  );
-});
diff --git a/packages/jest-runtime/src/index.ts b/packages/jest-runtime/src/index.ts
index b8f0a29e1fbf..346104f24b82 100644
--- a/packages/jest-runtime/src/index.ts
+++ b/packages/jest-runtime/src/index.ts
@@ -2265,21 +2265,10 @@ export default class Runtime {
     const isolateModulesAsync = this.isolateModulesAsync.bind(this);
     const fn = this._moduleMocker.fn.bind(this._moduleMocker);
     const spyOn = this._moduleMocker.spyOn.bind(this._moduleMocker);
-    const mocked =
-      this._moduleMocker.mocked?.bind(this._moduleMocker) ??
-      (() => {
-        throw new Error(
-          'Your test environment does not support `mocked`, please update it.',
-        );
-      });
-    const replaceProperty =
-      typeof this._moduleMocker.replaceProperty === 'function'
-        ? this._moduleMocker.replaceProperty.bind(this._moduleMocker)
-        : () => {
-            throw new Error(
-              'Your test environment does not support `jest.replaceProperty` - please ensure its Jest dependencies are updated to version 29.4 or later',
-            );
-          };
+    const mocked = this._moduleMocker.mocked.bind(this._moduleMocker);
+    const replaceProperty = this._moduleMocker.replaceProperty.bind(
+      this._moduleMocker,
+    );
 
     const setTimeout: Jest['setTimeout'] = timeout => {
       this._environment.global[testTimeoutSymbol] = timeout;
@@ -2305,12 +2294,6 @@ export default class Runtime {
         const fakeTimers = _getFakeTimers();
 
         if (fakeTimers === this._environment.fakeTimersModern) {
-          // TODO: remove this check in Jest 30
-          if (typeof fakeTimers.advanceTimersByTimeAsync !== 'function') {
-            throw new TypeError(
-              'Your test environment does not support async fake timers - please ensure its Jest dependencies are updated to version 29.5 or later',
-            );
-          }
           await fakeTimers.advanceTimersByTimeAsync(msToRun);
         } else {
           throw new TypeError(
@@ -2334,12 +2317,6 @@ export default class Runtime {
         const fakeTimers = _getFakeTimers();
 
         if (fakeTimers === this._environment.fakeTimersModern) {
-          // TODO: remove this check in Jest 30
-          if (typeof fakeTimers.advanceTimersToNextTimerAsync !== 'function') {
-            throw new TypeError(
-              'Your test environment does not support async fake timers - please ensure its Jest dependencies are updated to version 29.5 or later',
-            );
-          }
           await fakeTimers.advanceTimersToNextTimerAsync(steps);
         } else {
           throw new TypeError(
@@ -2369,15 +2346,7 @@ export default class Runtime {
           );
         }
       },
-      getSeed: () => {
-        // TODO: remove this check in Jest 30
-        if (this._globalConfig.seed === undefined) {
-          throw new Error(
-            'The seed value is not available. Likely you are using older versions of the jest dependencies.',
-          );
-        }
-        return this._globalConfig.seed;
-      },
+      getSeed: () => this._globalConfig.seed,
       getTimerCount: () => _getFakeTimers().getTimerCount(),
       isEnvironmentTornDown: () => this.isTornDown,
       isMockFunction: this._moduleMocker.isMockFunction,
@@ -2410,12 +2379,6 @@ export default class Runtime {
         const fakeTimers = _getFakeTimers();
 
         if (fakeTimers === this._environment.fakeTimersModern) {
-          // TODO: remove this check in Jest 30
-          if (typeof fakeTimers.runAllTimersAsync !== 'function') {
-            throw new TypeError(
-              'Your test environment does not support async fake timers - please ensure its Jest dependencies are updated to version 29.5 or later',
-            );
-          }
           await fakeTimers.runAllTimersAsync();
         } else {
           throw new TypeError(
@@ -2428,12 +2391,6 @@ export default class Runtime {
         const fakeTimers = _getFakeTimers();
 
         if (fakeTimers === this._environment.fakeTimersModern) {
-          // TODO: remove this check in Jest 30
-          if (typeof fakeTimers.runOnlyPendingTimersAsync !== 'function') {
-            throw new TypeError(
-              'Your test environment does not support async fake timers - please ensure its Jest dependencies are updated to version 29.5 or later',
-            );
-          }
           await fakeTimers.runOnlyPendingTimersAsync();
         } else {
           throw new TypeError(