diff --git a/packages/happy-dom/src/nodes/html-element/HTMLElement.ts b/packages/happy-dom/src/nodes/html-element/HTMLElement.ts
index 6022e22a9..feaa085a2 100644
--- a/packages/happy-dom/src/nodes/html-element/HTMLElement.ts
+++ b/packages/happy-dom/src/nodes/html-element/HTMLElement.ts
@@ -599,7 +599,23 @@ export default class HTMLElement extends Element {
 						}
 
 						if (newElement[PropertySymbol.isConnected] && newElement.connectedCallback) {
-							newElement.connectedCallback();
+							const result = <void | Promise<void>>newElement.connectedCallback();
+							/**
+							 * It is common to import dependencies in the connectedCallback() method of web components.
+							 * As Happy DOM doesn't have support for dynamic imports yet, this is a temporary solution to wait for imports in connectedCallback().
+							 *
+							 * @see https://github.com/capricorn86/happy-dom/issues/1442
+							 */
+							if (result instanceof Promise) {
+								const asyncTaskManager =
+									this[PropertySymbol.ownerDocument][PropertySymbol.ownerWindow][
+										PropertySymbol.asyncTaskManager
+									];
+								const taskID = asyncTaskManager.startTask();
+								result
+									.then(() => asyncTaskManager.endTask(taskID))
+									.catch(() => asyncTaskManager.endTask(taskID));
+							}
 						}
 
 						this[PropertySymbol.connectToNode](null);
diff --git a/packages/happy-dom/src/nodes/node/Node.ts b/packages/happy-dom/src/nodes/node/Node.ts
index 98094c4b9..2321df6e1 100644
--- a/packages/happy-dom/src/nodes/node/Node.ts
+++ b/packages/happy-dom/src/nodes/node/Node.ts
@@ -551,7 +551,23 @@ export default class Node extends EventTarget {
 			}
 
 			if (isConnected && this.connectedCallback) {
-				this.connectedCallback();
+				const result = <void | Promise<void>>this.connectedCallback();
+				/**
+				 * It is common to import dependencies in the connectedCallback() method of web components.
+				 * As Happy DOM doesn't have support for dynamic imports yet, this is a temporary solution to wait for imports in connectedCallback().
+				 *
+				 * @see https://github.com/capricorn86/happy-dom/issues/1442
+				 */
+				if (result instanceof Promise) {
+					const asyncTaskManager =
+						this[PropertySymbol.ownerDocument][PropertySymbol.ownerWindow][
+							PropertySymbol.asyncTaskManager
+						];
+					const taskID = asyncTaskManager.startTask();
+					result
+						.then(() => asyncTaskManager.endTask(taskID))
+						.catch(() => asyncTaskManager.endTask(taskID));
+				}
 			} else if (!isConnected && this.disconnectedCallback) {
 				this.disconnectedCallback();
 			}
diff --git a/packages/happy-dom/src/window/BrowserWindow.ts b/packages/happy-dom/src/window/BrowserWindow.ts
index 6213c76d9..8dc923d63 100644
--- a/packages/happy-dom/src/window/BrowserWindow.ts
+++ b/packages/happy-dom/src/window/BrowserWindow.ts
@@ -153,6 +153,7 @@ import RangeImplementation from '../range/Range.js';
 import INodeJSGlobal from './INodeJSGlobal.js';
 import CrossOriginBrowserWindow from './CrossOriginBrowserWindow.js';
 import Response from '../fetch/Response.js';
+import AsyncTaskManager from '../async-task-manager/AsyncTaskManager.js';
 
 const TIMER = {
 	setTimeout: globalThis.setTimeout.bind(globalThis),
@@ -495,6 +496,7 @@ export default class BrowserWindow extends EventTarget implements INodeJSGlobal
 	public [PropertySymbol.captureEventListenerCount]: { [eventType: string]: number } = {};
 	public readonly [PropertySymbol.mutationObservers]: MutationObserver[] = [];
 	public readonly [PropertySymbol.readyStateManager] = new DocumentReadyStateManager(this);
+	public [PropertySymbol.asyncTaskManager]: AsyncTaskManager | null = null;
 	public [PropertySymbol.location]: Location;
 	public [PropertySymbol.history]: History;
 	public [PropertySymbol.navigator]: Navigator;
@@ -520,6 +522,8 @@ export default class BrowserWindow extends EventTarget implements INodeJSGlobal
 	constructor(browserFrame: IBrowserFrame, options?: { url?: string }) {
 		super();
 
+		const asyncTaskManager = browserFrame[PropertySymbol.asyncTaskManager];
+
 		this.#browserFrame = browserFrame;
 
 		this.customElements = new CustomElementRegistry(this);
@@ -529,13 +533,13 @@ export default class BrowserWindow extends EventTarget implements INodeJSGlobal
 		this[PropertySymbol.sessionStorage] = StorageFactory.createStorage();
 		this[PropertySymbol.localStorage] = StorageFactory.createStorage();
 		this[PropertySymbol.location] = new Location(this.#browserFrame, options?.url ?? 'about:blank');
+		this[PropertySymbol.asyncTaskManager] = asyncTaskManager;
 
 		this.console = browserFrame.page.console;
 
 		WindowBrowserSettingsReader.setSettings(this, this.#browserFrame.page.context.browser.settings);
 
 		const window = this;
-		const asyncTaskManager = this.#browserFrame[PropertySymbol.asyncTaskManager];
 
 		this[PropertySymbol.setupVMContext]();
 
@@ -1302,6 +1306,7 @@ export default class BrowserWindow extends EventTarget implements INodeJSGlobal
 		}
 
 		(<boolean>this.closed) = true;
+		this[PropertySymbol.asyncTaskManager] = null;
 		this.Audio[PropertySymbol.ownerDocument] = null;
 		this.Image[PropertySymbol.ownerDocument] = null;
 		this.DocumentFragment[PropertySymbol.ownerDocument] = null;
diff --git a/packages/happy-dom/test/window/DetachedWindowAPI.test.ts b/packages/happy-dom/test/window/DetachedWindowAPI.test.ts
index e2e67de8a..c4737abde 100644
--- a/packages/happy-dom/test/window/DetachedWindowAPI.test.ts
+++ b/packages/happy-dom/test/window/DetachedWindowAPI.test.ts
@@ -87,7 +87,13 @@ describe('DetachedWindowAPI', () => {
 			});
 			window.clearInterval(intervalID);
 			window.setTimeout(() => {
-				tasksDone++;
+				window.setTimeout(() => {
+					window.setTimeout(() => {
+						window.setTimeout(() => {
+							tasksDone++;
+						});
+					});
+				});
 			});
 			window.setTimeout(() => {
 				tasksDone++;
@@ -100,7 +106,19 @@ describe('DetachedWindowAPI', () => {
 			});
 			window.fetch('/url/1/').then((response) => {
 				response.json().then(() => {
-					tasksDone++;
+					window.fetch('/url/1/').then((response) => {
+						response.json().then(() => {
+							window.fetch('/url/1/').then((response) => {
+								response.json().then(() => {
+									window.fetch('/url/1/').then((response) => {
+										response.json().then(() => {
+											tasksDone++;
+										});
+									});
+								});
+							});
+						});
+					});
 				});
 			});
 			window.fetch('/url/2/').then((response) => {
@@ -108,8 +126,36 @@ describe('DetachedWindowAPI', () => {
 					tasksDone++;
 				});
 			});
+
+			/**
+			 * It is common to import dependencies in the connectedCallback() method of web components.
+			 * As Happy DOM doesn't have support for dynamic imports yet, this is a temporary solution to wait for imports in connectedCallback().
+			 *
+			 * @see https://github.com/capricorn86/happy-dom/issues/1442
+			 */
+			class CustomElement extends window.HTMLElement {
+				/** */
+				public async connectedCallback(): Promise<void> {
+					await new Promise((resolve) => setTimeout(resolve, 200));
+					tasksDone++;
+				}
+			}
+			/** */
+			class CustomElement2 extends window.HTMLElement {
+				/** */
+				public async connectedCallback(): Promise<void> {
+					await new Promise((resolve) => setTimeout(resolve, 100));
+					tasksDone++;
+				}
+			}
+
+			window.customElements.define('custom-element', CustomElement);
+			window.document.body.appendChild(new CustomElement());
+			window.document.body.appendChild(window.document.createElement('custom-element-2'));
+			window.customElements.define('custom-element-2', CustomElement2);
+
 			await window.happyDOM?.waitUntilComplete();
-			expect(tasksDone).toBe(6);
+			expect(tasksDone).toBe(8);
 			expect(isFirstWhenAsyncCompleteCalled).toBe(true);
 		});
 	});