diff --git a/packages/react-dom/src/__tests__/ReactTestUtilsAct-test.js b/packages/react-dom/src/__tests__/ReactTestUtilsAct-test.js
index 556772500ee2f..71adc286d08ba 100644
--- a/packages/react-dom/src/__tests__/ReactTestUtilsAct-test.js
+++ b/packages/react-dom/src/__tests__/ReactTestUtilsAct-test.js
@@ -98,43 +98,12 @@ describe('ReactTestUtils.act()', () => {
       }).toErrorDev([]);
     });
 
-    it('warns in strict mode', () => {
-      expect(() => {
-        ReactDOM.render(
-          <React.StrictMode>
-            <App />
-          </React.StrictMode>,
-          document.createElement('div'),
-        );
-      }).toErrorDev([
-        'An update to App ran an effect, but was not wrapped in act(...)',
-      ]);
-    });
-
     // @gate __DEV__
     it('does not warn in concurrent mode', () => {
       const root = ReactDOM.createRoot(document.createElement('div'));
       act(() => root.render(<App />));
       Scheduler.unstable_flushAll();
     });
-
-    it('warns in concurrent mode if root is strict', () => {
-      // TODO: We don't need this error anymore in concurrent mode because
-      // effects can only be scheduled as the result of an update, and we now
-      // enforce all updates must be wrapped with act, not just hook updates.
-      expect(() => {
-        const root = ReactDOM.createRoot(document.createElement('div'), {
-          unstable_strictMode: true,
-        });
-        root.render(<App />);
-      }).toErrorDev(
-        'An update to Root inside a test was not wrapped in act(...)',
-        {withoutStack: true},
-      );
-      expect(() => Scheduler.unstable_flushAll()).toErrorDev(
-        'An update to App ran an effect, but was not wrapped in act(...)',
-      );
-    });
   });
 });
 
diff --git a/packages/react-reconciler/src/ReactFiberHooks.new.js b/packages/react-reconciler/src/ReactFiberHooks.new.js
index 266e98960cbb3..c3b76549a22aa 100644
--- a/packages/react-reconciler/src/ReactFiberHooks.new.js
+++ b/packages/react-reconciler/src/ReactFiberHooks.new.js
@@ -82,7 +82,6 @@ import {
   scheduleUpdateOnFiber,
   requestUpdateLane,
   requestEventTime,
-  warnIfNotCurrentlyActingEffectsInDEV,
   markSkippedUpdateLanes,
   isInterleavedUpdate,
 } from './ReactFiberWorkLoop.new';
@@ -1676,9 +1675,6 @@ function mountEffect(
   create: () => (() => void) | void,
   deps: Array<mixed> | void | null,
 ): void {
-  if (__DEV__) {
-    warnIfNotCurrentlyActingEffectsInDEV(currentlyRenderingFiber);
-  }
   if (
     __DEV__ &&
     enableStrictEffects &&
@@ -1704,9 +1700,6 @@ function updateEffect(
   create: () => (() => void) | void,
   deps: Array<mixed> | void | null,
 ): void {
-  if (__DEV__) {
-    warnIfNotCurrentlyActingEffectsInDEV(currentlyRenderingFiber);
-  }
   return updateEffectImpl(PassiveEffect, HookPassive, create, deps);
 }
 
diff --git a/packages/react-reconciler/src/ReactFiberHooks.old.js b/packages/react-reconciler/src/ReactFiberHooks.old.js
index b2378cbf30d65..8bc1510deb455 100644
--- a/packages/react-reconciler/src/ReactFiberHooks.old.js
+++ b/packages/react-reconciler/src/ReactFiberHooks.old.js
@@ -82,7 +82,6 @@ import {
   scheduleUpdateOnFiber,
   requestUpdateLane,
   requestEventTime,
-  warnIfNotCurrentlyActingEffectsInDEV,
   markSkippedUpdateLanes,
   isInterleavedUpdate,
 } from './ReactFiberWorkLoop.old';
@@ -1676,9 +1675,6 @@ function mountEffect(
   create: () => (() => void) | void,
   deps: Array<mixed> | void | null,
 ): void {
-  if (__DEV__) {
-    warnIfNotCurrentlyActingEffectsInDEV(currentlyRenderingFiber);
-  }
   if (
     __DEV__ &&
     enableStrictEffects &&
@@ -1704,9 +1700,6 @@ function updateEffect(
   create: () => (() => void) | void,
   deps: Array<mixed> | void | null,
 ): void {
-  if (__DEV__) {
-    warnIfNotCurrentlyActingEffectsInDEV(currentlyRenderingFiber);
-  }
   return updateEffectImpl(PassiveEffect, HookPassive, create, deps);
 }
 
diff --git a/packages/react-reconciler/src/ReactFiberWorkLoop.new.js b/packages/react-reconciler/src/ReactFiberWorkLoop.new.js
index 2c065d6ee17ab..e35e5515bb0bf 100644
--- a/packages/react-reconciler/src/ReactFiberWorkLoop.new.js
+++ b/packages/react-reconciler/src/ReactFiberWorkLoop.new.js
@@ -97,12 +97,7 @@ import {
   createWorkInProgress,
   assignFiberPropertiesInDEV,
 } from './ReactFiber.new';
-import {
-  NoMode,
-  StrictLegacyMode,
-  ProfileMode,
-  ConcurrentMode,
-} from './ReactTypeOfMode';
+import {NoMode, ProfileMode, ConcurrentMode} from './ReactTypeOfMode';
 import {
   HostRoot,
   IndeterminateComponent,
@@ -2860,34 +2855,6 @@ function shouldForceFlushFallbacksInDEV() {
   return __DEV__ && ReactCurrentActQueue.current !== null;
 }
 
-export function warnIfNotCurrentlyActingEffectsInDEV(fiber: Fiber): void {
-  if (__DEV__) {
-    const isActEnvironment =
-      fiber.mode & ConcurrentMode
-        ? isConcurrentActEnvironment()
-        : isLegacyActEnvironment(fiber);
-    if (
-      isActEnvironment &&
-      (fiber.mode & StrictLegacyMode) !== NoMode &&
-      ReactCurrentActQueue.current === null
-    ) {
-      console.error(
-        'An update to %s ran an effect, but was not wrapped in act(...).\n\n' +
-          'When testing, code that causes React state updates should be ' +
-          'wrapped into act(...):\n\n' +
-          'act(() => {\n' +
-          '  /* fire events that update state */\n' +
-          '});\n' +
-          '/* assert on the output */\n\n' +
-          "This ensures that you're testing the behavior the user would see " +
-          'in the browser.' +
-          ' Learn more at https://reactjs.org/link/wrap-tests-with-act',
-        getComponentNameFromFiber(fiber),
-      );
-    }
-  }
-}
-
 function warnIfUpdatesNotWrappedWithActDEV(fiber: Fiber): void {
   if (__DEV__) {
     if (fiber.mode & ConcurrentMode) {
diff --git a/packages/react-reconciler/src/ReactFiberWorkLoop.old.js b/packages/react-reconciler/src/ReactFiberWorkLoop.old.js
index 97b835d3a18e4..cde46adb01ab0 100644
--- a/packages/react-reconciler/src/ReactFiberWorkLoop.old.js
+++ b/packages/react-reconciler/src/ReactFiberWorkLoop.old.js
@@ -97,12 +97,7 @@ import {
   createWorkInProgress,
   assignFiberPropertiesInDEV,
 } from './ReactFiber.old';
-import {
-  NoMode,
-  StrictLegacyMode,
-  ProfileMode,
-  ConcurrentMode,
-} from './ReactTypeOfMode';
+import {NoMode, ProfileMode, ConcurrentMode} from './ReactTypeOfMode';
 import {
   HostRoot,
   IndeterminateComponent,
@@ -2860,34 +2855,6 @@ function shouldForceFlushFallbacksInDEV() {
   return __DEV__ && ReactCurrentActQueue.current !== null;
 }
 
-export function warnIfNotCurrentlyActingEffectsInDEV(fiber: Fiber): void {
-  if (__DEV__) {
-    const isActEnvironment =
-      fiber.mode & ConcurrentMode
-        ? isConcurrentActEnvironment()
-        : isLegacyActEnvironment(fiber);
-    if (
-      isActEnvironment &&
-      (fiber.mode & StrictLegacyMode) !== NoMode &&
-      ReactCurrentActQueue.current === null
-    ) {
-      console.error(
-        'An update to %s ran an effect, but was not wrapped in act(...).\n\n' +
-          'When testing, code that causes React state updates should be ' +
-          'wrapped into act(...):\n\n' +
-          'act(() => {\n' +
-          '  /* fire events that update state */\n' +
-          '});\n' +
-          '/* assert on the output */\n\n' +
-          "This ensures that you're testing the behavior the user would see " +
-          'in the browser.' +
-          ' Learn more at https://reactjs.org/link/wrap-tests-with-act',
-        getComponentNameFromFiber(fiber),
-      );
-    }
-  }
-}
-
 function warnIfUpdatesNotWrappedWithActDEV(fiber: Fiber): void {
   if (__DEV__) {
     if (fiber.mode & ConcurrentMode) {