diff --git a/packages/react/src/__tests__/ReactCoffeeScriptClass-test.coffee b/packages/react/src/__tests__/ReactCoffeeScriptClass-test.coffee
index 5bd9b24d52277..928ddb8959a5d 100644
--- a/packages/react/src/__tests__/ReactCoffeeScriptClass-test.coffee
+++ b/packages/react/src/__tests__/ReactCoffeeScriptClass-test.coffee
@@ -22,7 +22,6 @@ describe 'ReactCoffeeScriptClass', ->
     React = require 'react'
     ReactDOM = require 'react-dom'
     ReactDOMClient = require 'react-dom/client'
-    act = require('jest-react').act
     PropTypes = require 'prop-types'
     container = document.createElement 'div'
     root = ReactDOMClient.createRoot container
@@ -36,7 +35,7 @@ describe 'ReactCoffeeScriptClass', ->
         return React.createElement('div', className: this.props.name)
 
   test = (element, expectedTag, expectedClassName) ->
-    act ->
+    ReactDOM.flushSync ->
       root.render(element)
     expect(container.firstChild).not.toBeNull()
     expect(container.firstChild.tagName).toBe(expectedTag)
@@ -50,7 +49,7 @@ describe 'ReactCoffeeScriptClass', ->
     class Foo extends React.Component
     expect(->
       expect(->
-        act ->
+        ReactDOM.flushSync ->
           root.render React.createElement(Foo)
       ).toThrow()
     ).toErrorDev([
@@ -103,7 +102,8 @@ describe 'ReactCoffeeScriptClass', ->
 
     ref = React.createRef()
     test React.createElement(Foo, initialValue: 'foo', ref: ref), 'DIV', 'foo'
-    ref.current.changeState()
+    ReactDOM.flushSync ->
+      ref.current.changeState()
     test React.createElement(Foo), 'SPAN', 'bar'
 
   it 'sets initial state with value returned by static getDerivedStateFromProps', ->
@@ -129,7 +129,7 @@ describe 'ReactCoffeeScriptClass', ->
       getDerivedStateFromProps: ->
         {}
     expect(->
-      act ->
+      ReactDOM.flushSync ->
         root.render React.createElement(Foo, foo: 'foo')
       return
     ).toErrorDev 'Foo: getDerivedStateFromProps() is defined as an instance method and will be ignored. Instead, declare it as a static method.'
@@ -141,7 +141,7 @@ describe 'ReactCoffeeScriptClass', ->
       getDerivedStateFromError: ->
         {}
     expect(->
-      act ->
+      ReactDOM.flushSync ->
         root.render React.createElement(Foo, foo: 'foo')
       return
     ).toErrorDev 'Foo: getDerivedStateFromError() is defined as an instance method and will be ignored. Instead, declare it as a static method.'
@@ -153,7 +153,7 @@ describe 'ReactCoffeeScriptClass', ->
     Foo.getSnapshotBeforeUpdate = () ->
       {}
     expect(->
-      act ->
+      ReactDOM.flushSync ->
         root.render React.createElement(Foo, foo: 'foo')
       return
     ).toErrorDev 'Foo: getSnapshotBeforeUpdate() is defined as a static method and will be ignored. Instead, declare it as an instance method.'
@@ -170,7 +170,7 @@ describe 'ReactCoffeeScriptClass', ->
         bar: 'bar'
       }
     expect(->
-      act ->
+      ReactDOM.flushSync ->
         root.render React.createElement(Foo, foo: 'foo')
       return
     ).toErrorDev (
@@ -303,7 +303,7 @@ describe 'ReactCoffeeScriptClass', ->
         )
 
     test React.createElement(Foo, initialValue: 'foo'), 'DIV', 'foo'
-    act ->
+    ReactDOM.flushSync ->
       attachedListener()
     expect(renderedName).toBe 'bar'
 
@@ -340,7 +340,7 @@ describe 'ReactCoffeeScriptClass', ->
         )
 
     test React.createElement(Foo, initialValue: 'foo'), 'DIV', 'foo'
-    act ->
+    ReactDOM.flushSync ->
       attachedListener()
     expect(renderedName).toBe 'bar'
 
@@ -391,7 +391,7 @@ describe 'ReactCoffeeScriptClass', ->
       'did-update',    { value: 'foo' }, {}
     ]
     lifeCycles = [] # reset
-    act ->
+    ReactDOM.flushSync ->
       root.unmount()
     expect(lifeCycles).toEqual ['will-unmount']
 
diff --git a/packages/react/src/__tests__/ReactES6Class-test.js b/packages/react/src/__tests__/ReactES6Class-test.js
index 62f020849489f..70944b398dcbd 100644
--- a/packages/react/src/__tests__/ReactES6Class-test.js
+++ b/packages/react/src/__tests__/ReactES6Class-test.js
@@ -13,7 +13,6 @@ let PropTypes;
 let React;
 let ReactDOM;
 let ReactDOMClient;
-let act;
 
 describe('ReactES6Class', () => {
   let container;
@@ -31,7 +30,6 @@ describe('ReactES6Class', () => {
     React = require('react');
     ReactDOM = require('react-dom');
     ReactDOMClient = require('react-dom/client');
-    act = require('jest-react').act;
     container = document.createElement('div');
     root = ReactDOMClient.createRoot(container);
     attachedListener = null;
@@ -49,7 +47,7 @@ describe('ReactES6Class', () => {
   });
 
   function test(element, expectedTag, expectedClassName) {
-    act(() => root.render(element));
+    ReactDOM.flushSync(() => root.render(element));
     expect(container.firstChild).not.toBeNull();
     expect(container.firstChild.tagName).toBe(expectedTag);
     expect(container.firstChild.className).toBe(expectedClassName);
@@ -63,7 +61,7 @@ describe('ReactES6Class', () => {
   it('throws if no render function is defined', () => {
     class Foo extends React.Component {}
     expect(() => {
-      expect(() => act(() => root.render(<Foo />))).toThrow();
+      expect(() => ReactDOM.flushSync(() => root.render(<Foo />))).toThrow();
     }).toErrorDev([
       // A failed component renders four times in DEV in concurrent mode
       'Warning: Foo(...): No `render` method found on the returned component ' +
@@ -118,7 +116,7 @@ describe('ReactES6Class', () => {
     }
     const ref = React.createRef();
     test(<Foo initialValue="foo" ref={ref} />, 'DIV', 'foo');
-    act(() => ref.current.changeState());
+    ReactDOM.flushSync(() => ref.current.changeState());
     test(<Foo />, 'SPAN', 'bar');
   });
 
@@ -148,7 +146,7 @@ describe('ReactES6Class', () => {
       }
     }
     expect(() => {
-      act(() => root.render(<Foo foo="foo" />));
+      ReactDOM.flushSync(() => root.render(<Foo foo="foo" />));
     }).toErrorDev(
       'Foo: getDerivedStateFromProps() is defined as an instance method ' +
         'and will be ignored. Instead, declare it as a static method.',
@@ -165,7 +163,7 @@ describe('ReactES6Class', () => {
       }
     }
     expect(() => {
-      act(() => root.render(<Foo foo="foo" />));
+      ReactDOM.flushSync(() => root.render(<Foo foo="foo" />));
     }).toErrorDev(
       'Foo: getDerivedStateFromError() is defined as an instance method ' +
         'and will be ignored. Instead, declare it as a static method.',
@@ -180,7 +178,7 @@ describe('ReactES6Class', () => {
       }
     }
     expect(() => {
-      act(() => root.render(<Foo foo="foo" />));
+      ReactDOM.flushSync(() => root.render(<Foo foo="foo" />));
     }).toErrorDev(
       'Foo: getSnapshotBeforeUpdate() is defined as a static method ' +
         'and will be ignored. Instead, declare it as an instance method.',
@@ -200,7 +198,7 @@ describe('ReactES6Class', () => {
       }
     }
     expect(() => {
-      act(() => root.render(<Foo foo="foo" />));
+      ReactDOM.flushSync(() => root.render(<Foo foo="foo" />));
     }).toErrorDev(
       '`Foo` uses `getDerivedStateFromProps` but its initial state is ' +
         'undefined. This is not recommended. Instead, define the initial state by ' +
@@ -347,7 +345,7 @@ describe('ReactES6Class', () => {
     }
     test(<Foo initialValue="foo" />, 'DIV', 'foo');
 
-    act(() => attachedListener());
+    ReactDOM.flushSync(() => attachedListener());
     expect(renderedName).toBe('bar');
   });
 
@@ -388,7 +386,7 @@ describe('ReactES6Class', () => {
       }
     }
     test(<Foo initialValue="foo" />, 'DIV', 'foo');
-    act(() => attachedListener());
+    ReactDOM.flushSync(() => attachedListener());
     expect(renderedName).toBe('bar');
   });
 
@@ -437,7 +435,7 @@ describe('ReactES6Class', () => {
       'did-update', freeze({value: 'foo'}), {},
     ]);
     lifeCycles = []; // reset
-    act(() => root.unmount());
+    ReactDOM.flushSync(() => root.unmount());
     expect(lifeCycles).toEqual(['will-unmount']);
   });
 
diff --git a/packages/react/src/__tests__/ReactTypeScriptClass-test.ts b/packages/react/src/__tests__/ReactTypeScriptClass-test.ts
index dfea3cea47b3f..efaac47524efb 100644
--- a/packages/react/src/__tests__/ReactTypeScriptClass-test.ts
+++ b/packages/react/src/__tests__/ReactTypeScriptClass-test.ts
@@ -16,7 +16,6 @@ import ReactDOM = require('react-dom');
 import ReactDOMClient = require('react-dom/client');
 import ReactDOMTestUtils = require('react-dom/test-utils');
 import PropTypes = require('prop-types');
-import internalAct = require('jest-react');
 
 // Before Each
 
@@ -24,7 +23,6 @@ let container;
 let root;
 let attachedListener = null;
 let renderedName = null;
-let act = internalAct.act;
 
 class Inner extends React.Component {
   getName() {
@@ -38,7 +36,7 @@ class Inner extends React.Component {
 }
 
 function test(element, expectedTag, expectedClassName) {
-  act(() => root.render(element));
+  ReactDOM.flushSync(() => root.render(element));
   expect(container.firstChild).not.toBeNull();
   expect(container.firstChild.tagName).toBe(expectedTag);
   expect(container.firstChild.className).toBe(expectedClassName);
@@ -331,7 +329,7 @@ describe('ReactTypeScriptClass', function() {
   it('throws if no render function is defined', function() {
     expect(() => {
       expect(() =>
-        act(() => root.render(React.createElement(Empty)))
+        ReactDOM.flushSync(() => root.render(React.createElement(Empty)))
       ).toThrow();
     }).toErrorDev([
       // A failed component renders four times in DEV in concurrent mode
@@ -366,7 +364,7 @@ describe('ReactTypeScriptClass', function() {
       'DIV',
       'foo'
     );
-    act(() => ref.current.changeState());
+    ReactDOM.flushSync(() => ref.current.changeState());
     test(React.createElement(StateBasedOnProps), 'SPAN', 'bar');
   });
 
@@ -401,7 +399,7 @@ describe('ReactTypeScriptClass', function() {
       }
     }
     expect(function() {
-      act(() =>
+      ReactDOM.flushSync(() =>
         root.render(React.createElement(Foo, {foo: 'foo'}))
       );
     }).toErrorDev(
@@ -420,7 +418,7 @@ describe('ReactTypeScriptClass', function() {
       }
     }
     expect(function() {
-      act(() =>
+      ReactDOM.flushSync(() =>
         root.render(React.createElement(Foo, {foo: 'foo'}))
       );
     }).toErrorDev(
@@ -437,7 +435,7 @@ describe('ReactTypeScriptClass', function() {
       }
     }
     expect(function() {
-      act(() =>
+      ReactDOM.flushSync(() =>
         root.render(React.createElement(Foo, {foo: 'foo'}))
       );
     }).toErrorDev(
@@ -461,7 +459,7 @@ describe('ReactTypeScriptClass', function() {
       }
     }
     expect(function() {
-      act(() =>
+      ReactDOM.flushSync(() =>
         root.render(React.createElement(Foo, {foo: 'foo'}))
       );
     }).toErrorDev(
@@ -547,7 +545,7 @@ describe('ReactTypeScriptClass', function() {
       'DIV',
       'foo'
     );
-    act(() => attachedListener());
+    ReactDOM.flushSync(() => attachedListener());
     expect(renderedName).toBe('bar');
   });
 
@@ -566,7 +564,7 @@ describe('ReactTypeScriptClass', function() {
       'DIV',
       'foo'
     );
-    act(() => attachedListener());
+    ReactDOM.flushSync(() => attachedListener());
     expect(renderedName).toBe('bar');
   });
 
@@ -590,7 +588,7 @@ describe('ReactTypeScriptClass', function() {
       {},
     ]);
     lifeCycles = []; // reset
-    act(() => root.unmount(container));
+    ReactDOM.flushSync(() => root.unmount(container));
     expect(lifeCycles).toEqual(['will-unmount']);
   });
 
diff --git a/packages/react/src/__tests__/testDefinitions/ReactDOM.d.ts b/packages/react/src/__tests__/testDefinitions/ReactDOM.d.ts
index 0b20d827b4514..eb6ad709efb1a 100644
--- a/packages/react/src/__tests__/testDefinitions/ReactDOM.d.ts
+++ b/packages/react/src/__tests__/testDefinitions/ReactDOM.d.ts
@@ -16,4 +16,5 @@ declare module 'react-dom' {
   export function render(element : any, container : any) : any
   export function unmountComponentAtNode(container : any) : void
   export function findDOMNode(instance : any) : any
+  export function flushSync(cb : any) : any
 }