diff --git a/extensions/markdown-language-features/src/features/preview.ts b/extensions/markdown-language-features/src/features/preview.ts
index 4ecef4ac7b699..d9bcd0bb00d17 100644
--- a/extensions/markdown-language-features/src/features/preview.ts
+++ b/extensions/markdown-language-features/src/features/preview.ts
@@ -161,6 +161,10 @@ export class MarkdownPreview extends Disposable {
 			this._onDidChangeViewStateEmitter.fire(e);
 		}, null, this._disposables);
 
+		_contributionProvider.onContributionsChanged(() => {
+			setImmediate(() => this.refresh());
+		}, null, this._disposables);
+
 		this.editor.webview.onDidReceiveMessage((e: CacheImageSizesMessage | RevealLineMessage | DidClickMessage | ClickLinkMessage | ShowPreviewSecuritySelectorMessage | PreviewStyleLoadErrorMessage) => {
 			if (e.source !== this._resource.toString()) {
 				return;
diff --git a/extensions/markdown-language-features/src/markdownEngine.ts b/extensions/markdown-language-features/src/markdownEngine.ts
index 090c8ab0da464..c26eb4834b82e 100644
--- a/extensions/markdown-language-features/src/markdownEngine.ts
+++ b/extensions/markdown-language-features/src/markdownEngine.ts
@@ -59,14 +59,19 @@ export class MarkdownEngine {
 	public constructor(
 		private readonly contributionProvider: MarkdownContributionProvider,
 		private readonly slugifier: Slugifier,
-	) { }
+	) {
+		contributionProvider.onContributionsChanged(() => {
+			// Markdown plugin contributions may have changed
+			this.md = undefined;
+		});
+	}
 
 	private async getEngine(config: MarkdownItConfig): Promise<MarkdownIt> {
 		if (!this.md) {
 			this.md = import('markdown-it').then(async markdownIt => {
 				let md: MarkdownIt = markdownIt(await getMarkdownOptions(() => md));
 
-				for (const plugin of this.contributionProvider.contributions.markdownItPlugins) {
+				for (const plugin of this.contributionProvider.contributions.markdownItPlugins.values()) {
 					try {
 						md = (await plugin)(md);
 					} catch {
diff --git a/extensions/markdown-language-features/src/markdownExtensions.ts b/extensions/markdown-language-features/src/markdownExtensions.ts
index 4ca972f5c701b..567ee946b9d17 100644
--- a/extensions/markdown-language-features/src/markdownExtensions.ts
+++ b/extensions/markdown-language-features/src/markdownExtensions.ts
@@ -5,6 +5,8 @@
 
 import * as vscode from 'vscode';
 import * as path from 'path';
+import { Disposable } from './util/dispose';
+import * as arrays from './util/arrays';
 
 const resolveExtensionResource = (extension: vscode.Extension<any>, resourcePath: string): vscode.Uri => {
 	return vscode.Uri.file(path.join(extension.extensionPath, resourcePath))
@@ -29,7 +31,7 @@ export interface MarkdownContributions {
 	readonly previewScripts: ReadonlyArray<vscode.Uri>;
 	readonly previewStyles: ReadonlyArray<vscode.Uri>;
 	readonly previewResourceRoots: ReadonlyArray<vscode.Uri>;
-	readonly markdownItPlugins: ReadonlyArray<Thenable<(md: any) => any>>;
+	readonly markdownItPlugins: Map<string, Thenable<(md: any) => any>>;
 }
 
 export namespace MarkdownContributions {
@@ -37,7 +39,7 @@ export namespace MarkdownContributions {
 		previewScripts: [],
 		previewStyles: [],
 		previewResourceRoots: [],
-		markdownItPlugins: []
+		markdownItPlugins: new Map()
 	};
 
 	export function merge(a: MarkdownContributions, b: MarkdownContributions): MarkdownContributions {
@@ -45,10 +47,21 @@ export namespace MarkdownContributions {
 			previewScripts: [...a.previewScripts, ...b.previewScripts],
 			previewStyles: [...a.previewStyles, ...b.previewStyles],
 			previewResourceRoots: [...a.previewResourceRoots, ...b.previewResourceRoots],
-			markdownItPlugins: [...a.markdownItPlugins, ...b.markdownItPlugins],
+			markdownItPlugins: new Map([...a.markdownItPlugins.entries(), ...b.markdownItPlugins.entries()]),
 		};
 	}
 
+	function uriEqual(a: vscode.Uri, b: vscode.Uri): boolean {
+		return a.toString() === b.toString();
+	}
+
+	export function equal(a: MarkdownContributions, b: MarkdownContributions): boolean {
+		return arrays.equals(a.previewScripts, b.previewScripts, uriEqual)
+			&& arrays.equals(a.previewStyles, b.previewStyles, uriEqual)
+			&& arrays.equals(a.previewResourceRoots, b.previewResourceRoots, uriEqual)
+			&& arrays.equals(Array.from(a.markdownItPlugins.keys()), Array.from(b.markdownItPlugins.keys()));
+	}
+
 	export function fromExtension(
 		extension: vscode.Extension<any>
 	): MarkdownContributions {
@@ -69,7 +82,7 @@ export namespace MarkdownContributions {
 			previewScripts: scripts,
 			previewStyles: styles,
 			previewResourceRoots,
-			markdownItPlugins: plugins ? [plugins] : []
+			markdownItPlugins: plugins ? new Map([[extension.id, plugins]]) : new Map()
 		};
 	}
 
@@ -106,23 +119,42 @@ export namespace MarkdownContributions {
 export interface MarkdownContributionProvider {
 	readonly extensionPath: string;
 	readonly contributions: MarkdownContributions;
+	readonly onContributionsChanged: vscode.Event<this>;
 }
 
-class VSCodeExtensionMarkdownContributionProvider implements MarkdownContributionProvider {
+class VSCodeExtensionMarkdownContributionProvider extends Disposable implements MarkdownContributionProvider {
 	private _contributions?: MarkdownContributions;
 
 	public constructor(
 		public readonly extensionPath: string,
-	) { }
+	) {
+		super();
+
+		vscode.extensions.onDidChange(() => {
+			const currentContributions = this.getCurrentContributions();
+			const existingContributions = this._contributions || MarkdownContributions.Empty;
+			if (!MarkdownContributions.equal(existingContributions, currentContributions)) {
+				this._contributions = currentContributions;
+				this._onContributionsChanged.fire(this);
+			}
+		}, undefined, this._disposables);
+	}
+
+	private readonly _onContributionsChanged = new vscode.EventEmitter<this>();
+	public readonly onContributionsChanged = this._onContributionsChanged.event;
 
 	public get contributions(): MarkdownContributions {
 		if (!this._contributions) {
-			this._contributions = vscode.extensions.all.reduce(
-				(contributions, extension) => MarkdownContributions.merge(contributions, MarkdownContributions.fromExtension(extension)),
-				MarkdownContributions.Empty);
+			this._contributions = this.getCurrentContributions();
 		}
 		return this._contributions;
 	}
+
+	private getCurrentContributions(): MarkdownContributions {
+		return vscode.extensions.all
+			.map(MarkdownContributions.fromExtension)
+			.reduce(MarkdownContributions.merge, MarkdownContributions.Empty);
+	}
 }
 
 export function getMarkdownExtensionContributions(context: vscode.ExtensionContext): MarkdownContributionProvider {
diff --git a/extensions/markdown-language-features/src/test/engine.ts b/extensions/markdown-language-features/src/test/engine.ts
index 1a674c8a50900..fef334b4cf54b 100644
--- a/extensions/markdown-language-features/src/test/engine.ts
+++ b/extensions/markdown-language-features/src/test/engine.ts
@@ -3,6 +3,7 @@
  *  Licensed under the MIT License. See License.txt in the project root for license information.
  *--------------------------------------------------------------------------------------------*/
 
+import * as vscode from 'vscode';
 import { MarkdownEngine } from '../markdownEngine';
 import { MarkdownContributionProvider, MarkdownContributions } from '../markdownExtensions';
 import { githubSlugifier } from '../slugify';
@@ -10,6 +11,7 @@ import { githubSlugifier } from '../slugify';
 const emptyContributions = new class implements MarkdownContributionProvider {
 	readonly extensionPath = '';
 	readonly contributions = MarkdownContributions.Empty;
+	readonly onContributionsChanged = new vscode.EventEmitter<this>().event;
 };
 
 export function createNewMarkdownEngine(): MarkdownEngine {
diff --git a/extensions/markdown-language-features/src/util/arrays.ts b/extensions/markdown-language-features/src/util/arrays.ts
new file mode 100644
index 0000000000000..10599259901a7
--- /dev/null
+++ b/extensions/markdown-language-features/src/util/arrays.ts
@@ -0,0 +1,18 @@
+/*---------------------------------------------------------------------------------------------
+ *  Copyright (c) Microsoft Corporation. All rights reserved.
+ *  Licensed under the MIT License. See License.txt in the project root for license information.
+ *--------------------------------------------------------------------------------------------*/
+
+export function equals<T>(one: ReadonlyArray<T>, other: ReadonlyArray<T>, itemEquals: (a: T, b: T) => boolean = (a, b) => a === b): boolean {
+	if (one.length !== other.length) {
+		return false;
+	}
+
+	for (let i = 0, len = one.length; i < len; i++) {
+		if (!itemEquals(one[i], other[i])) {
+			return false;
+		}
+	}
+
+	return true;
+}