diff --git a/definitions/environments/node/flow_v0.155.x-/node.js b/definitions/environments/node/flow_v0.155.x-/node.js
index 59a9ff7cb1..1c23ccf9f1 100644
--- a/definitions/environments/node/flow_v0.155.x-/node.js
+++ b/definitions/environments/node/flow_v0.155.x-/node.js
@@ -47,3 +47,146 @@ declare module 'node:util' {
 declare module 'node:url' {
   declare module.exports: $Exports<'url'>;
 }
+
+declare module 'worker_threads' {
+  declare var isMainThread: boolean;
+  declare var parentPort: null | MessagePort;
+  declare var threadId: number;
+  declare var workerData: any;
+
+  declare class MessageChannel {
+    +port1: MessagePort;
+    +port2: MessagePort;
+  }
+
+  declare class MessagePort extends events$EventEmitter {
+    close(): void;
+    postMessage(value: any, transferList?: Array<ArrayBuffer | MessagePort>): void;
+    ref(): void;
+    unref(): void;
+    start(): void;
+
+    addListener(event: "close", listener: () => void): this;
+    addListener(event: "message", listener: (value: any) => void): this;
+    addListener(event: string | Symbol, listener: (...args: any[]) => void): this;
+
+    emit(event: "close"): boolean;
+    emit(event: "message", value: any): boolean;
+    emit(event: string | Symbol, ...args: any[]): boolean;
+
+    on(event: "close", listener: () => void): this;
+    on(event: "message", listener: (value: any) => void): this;
+    on(event: string | Symbol, listener: (...args: any[]) => void): this;
+
+    once(event: "close", listener: () => void): this;
+    once(event: "message", listener: (value: any) => void): this;
+    once(event: string | Symbol, listener: (...args: any[]) => void): this;
+
+    prependListener(event: "close", listener: () => void): this;
+    prependListener(event: "message", listener: (value: any) => void): this;
+    prependListener(event: string | Symbol, listener: (...args: any[]) => void): this;
+
+    prependOnceListener(event: "close", listener: () => void): this;
+    prependOnceListener(event: "message", listener: (value: any) => void): this;
+    prependOnceListener(event: string | Symbol, listener: (...args: any[]) => void): this;
+
+    removeListener(event: "close", listener: () => void): this;
+    removeListener(event: "message", listener: (value: any) => void): this;
+    removeListener(event: string | Symbol, listener: (...args: any[]) => void): this;
+
+    off(event: "close", listener: () => void): this;
+    off(event: "message", listener: (value: any) => void): this;
+    off(event: string | Symbol, listener: (...args: any[]) => void): this;
+  }
+
+  declare type WorkerOptions = {|
+    env?: Object,
+    eval?: boolean,
+    workerData?: any,
+    stdin?: boolean,
+    stdout?: boolean,
+    stderr?: boolean,
+    execArgv?: string[]
+  |}
+
+  declare class Worker extends events$EventEmitter {
+    +stdin: stream$Writable | null;
+    +stdout: stream$Readable;
+    +stderr: stream$Readable;
+    +threadId: number;
+
+    constructor(filename: string, options?: WorkerOptions): void;
+
+    postMessage(value: any, transferList?: Array<ArrayBuffer | MessagePort>): void;
+    ref(): void;
+    unref(): void;
+    terminate(callback?: (err: Error, exitCode: number) => void): void;
+    /**
+     * Transfer a `MessagePort` to a different `vm` Context. The original `port`
+     * object will be rendered unusable, and the returned `MessagePort` instance will
+     * take its place.
+     *
+     * The returned `MessagePort` will be an object in the target context, and will
+     * inherit from its global `Object` class. Objects passed to the
+     * `port.onmessage()` listener will also be created in the target context
+     * and inherit from its global `Object` class.
+     *
+     * However, the created `MessagePort` will no longer inherit from
+     * `EventEmitter`, and only `port.onmessage()` can be used to receive
+     * events using it.
+     */
+    moveMessagePortToContext(port: MessagePort, context: vm$Context): MessagePort;
+
+    addListener(event: "error", listener: (err: Error) => void): this;
+    addListener(event: "exit", listener: (exitCode: number) => void): this;
+    addListener(event: "message", listener: (value: any) => void): this;
+    addListener(event: "online", listener: () => void): this;
+    addListener(event: string | Symbol, listener: (...args: any[]) => void): this;
+
+    emit(event: "error", err: Error): boolean;
+    emit(event: "exit", exitCode: number): boolean;
+    emit(event: "message", value: any): boolean;
+    emit(event: "online"): boolean;
+    emit(event: string | Symbol, ...args: any[]): boolean;
+
+    on(event: "error", listener: (err: Error) => void): this;
+    on(event: "exit", listener: (exitCode: number) => void): this;
+    on(event: "message", listener: (value: any) => void): this;
+    on(event: "online", listener: () => void): this;
+    on(event: string | Symbol, listener: (...args: any[]) => void): this;
+
+    once(event: "error", listener: (err: Error) => void): this;
+    once(event: "exit", listener: (exitCode: number) => void): this;
+    once(event: "message", listener: (value: any) => void): this;
+    once(event: "online", listener: () => void): this;
+    once(event: string | Symbol, listener: (...args: any[]) => void): this;
+
+    prependListener(event: "error", listener: (err: Error) => void): this;
+    prependListener(event: "exit", listener: (exitCode: number) => void): this;
+    prependListener(event: "message", listener: (value: any) => void): this;
+    prependListener(event: "online", listener: () => void): this;
+    prependListener(event: string | Symbol, listener: (...args: any[]) => void): this;
+
+    prependOnceListener(event: "error", listener: (err: Error) => void): this;
+    prependOnceListener(event: "exit", listener: (exitCode: number) => void): this;
+    prependOnceListener(event: "message", listener: (value: any) => void): this;
+    prependOnceListener(event: "online", listener: () => void): this;
+    prependOnceListener(event: string | Symbol, listener: (...args: any[]) => void): this;
+
+    removeListener(event: "error", listener: (err: Error) => void): this;
+    removeListener(event: "exit", listener: (exitCode: number) => void): this;
+    removeListener(event: "message", listener: (value: any) => void): this;
+    removeListener(event: "online", listener: () => void): this;
+    removeListener(event: string | Symbol, listener: (...args: any[]) => void): this;
+
+    off(event: "error", listener: (err: Error) => void): this;
+    off(event: "exit", listener: (exitCode: number) => void): this;
+    off(event: "message", listener: (value: any) => void): this;
+    off(event: "online", listener: () => void): this;
+    off(event: string | Symbol, listener: (...args: any[]) => void): this;
+  }
+}
+
+declare module 'node:worker_threads' {
+  declare module.exports: $Exports<'worker_threads'>;
+}
diff --git a/definitions/environments/node/flow_v0.155.x-/test_node.js b/definitions/environments/node/flow_v0.155.x-/test_node.js
index 8aee4acb72..3ffe61db12 100644
--- a/definitions/environments/node/flow_v0.155.x-/test_node.js
+++ b/definitions/environments/node/flow_v0.155.x-/test_node.js
@@ -1,5 +1,5 @@
 // @flow
-import { describe, it } from 'flow-typed-test';
+import { describe, it, test } from 'flow-typed-test';
 
 import assert from 'assert';
 import events from 'events';
@@ -8,6 +8,10 @@ import os from 'os';
 import path from 'path';
 import util from 'util';
 import url from 'url';
+import {
+  Worker,
+  isMainThread,
+} from 'worker_threads';
 
 import nodeAssert from 'node:assert';
 import nodeAssertStrict from 'node:assert/strict';
@@ -21,6 +25,10 @@ import nodeOs from 'node:os';
 import nodePath from 'node:path';
 import nodeUtil from 'node:util';
 import nodeUrl from 'node:url';
+import {
+  Worker as nodeWorker,
+  isMainThread as nodeIsMainThread,
+} from 'node:worker_threads';
 
 describe('node', () => {
   describe('node:assert', () => {
@@ -110,4 +118,36 @@ describe('node', () => {
       (nodeUrl.pathToFileURL: typeof url.pathToFileURL);
     });
   });
+
+  describe('worker_threads', () => {
+    test('Worker', () => {
+      const worker = new Worker('filename', {
+        workerData: 'test',
+      });
+      worker.on('message', () => {});
+      worker.on('error', () => {});
+    });
+
+    test('isMainThread', () => {
+      (isMainThread: boolean);
+      // $FlowExpectedError[incompatible-cast]
+      (isMainThread: string);
+    });
+  });
+
+  describe('node:worker_threads', () => {
+    test('Worker', () => {
+      const worker = new nodeWorker('filename', {
+        workerData: 'test',
+      });
+      worker.on('message', () => {});
+      worker.on('error', () => {});
+    });
+
+    test('isMainThread', () => {
+      (nodeIsMainThread: boolean);
+      // $FlowExpectedError[incompatible-cast]
+      (nodeIsMainThread: string);
+    });
+  });
 });