diff --git a/front_end/component_docs/tree_outline/BUILD.gn b/front_end/component_docs/tree_outline/BUILD.gn
index b2d9cae27c..109420aeea 100644
--- a/front_end/component_docs/tree_outline/BUILD.gn
+++ b/front_end/component_docs/tree_outline/BUILD.gn
@@ -9,6 +9,7 @@ ts_library("ts") {
   testonly = true
   sources = [
     "basic.ts",
+    "custom-renderers.ts",
     "lazy-children.ts",
     "sample-data.ts",
   ]
@@ -16,6 +17,7 @@ ts_library("ts") {
   deps = [
     "../../../test/unittests/front_end/helpers",
     "../../component_helpers:bundle",
+    "../../third_party/lit-html:bundle",
     "../../ui/components:bundle",
   ]
 }
@@ -24,6 +26,7 @@ copy_to_gen("tree_outline") {
   testonly = true
   sources = [
     "basic.html",
+    "custom-renderers.html",
     "lazy-children.html",
   ]
 
diff --git a/front_end/component_docs/tree_outline/custom-renderers.html b/front_end/component_docs/tree_outline/custom-renderers.html
new file mode 100644
index 0000000000..e5b231c8a8
--- /dev/null
+++ b/front_end/component_docs/tree_outline/custom-renderers.html
@@ -0,0 +1,32 @@
+<!--
+  Copyright 2020 The Chromium Authors. All rights reserved.
+  Use of this source code is governed by a BSD-style license that can be
+  found in the LICENSE file.
+-->
+<!DOCTYPE html>
+<html>
+  <head>
+    <meta charset="UTF-8" />
+    <meta name="viewport" content="width=device-width" />
+    <title>TreeOutline with custom renderers</title>
+    <style>
+      #container {
+        width: 80%;
+        border: 1px solid black;
+        padding: 20px;
+        height: 300px;
+      }
+    </style>
+  </head>
+
+  <body>
+
+    <div id="container">
+    </div>
+
+    <button id="recursively-expand">Recursively expand</button>
+
+
+    <script type="module" src="./custom-renderers.js"></script>
+  </body>
+</html>
diff --git a/front_end/component_docs/tree_outline/custom-renderers.ts b/front_end/component_docs/tree_outline/custom-renderers.ts
new file mode 100644
index 0000000000..0eaf98c4b3
--- /dev/null
+++ b/front_end/component_docs/tree_outline/custom-renderers.ts
@@ -0,0 +1,70 @@
+// Copyright 2020 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+import * as FrontendHelpers from '../../../test/unittests/front_end/helpers/EnvironmentHelpers.js';
+import * as ComponentHelpers from '../../component_helpers/component_helpers.js';
+import * as LitHtml from '../../third_party/lit-html/lit-html.js';
+import * as Components from '../../ui/components/components.js';
+
+await ComponentHelpers.ComponentServerSetup.setup();
+await FrontendHelpers.initializeGlobalVars();
+
+const data: Components.TreeOutline.TreeOutlineData = {
+  tree: [
+    {
+      key: 'Offices',
+      renderer: (key: string): LitHtml.TemplateResult =>
+          LitHtml.html`<strong style="color:red;">${key.toUpperCase()}</strong>`,
+      children: (): Promise<Components.TreeOutlineUtils.TreeNode[]> => Promise.resolve([
+        {
+          key: 'Europe',
+          children: (): Promise<Components.TreeOutlineUtils.TreeNode[]> => Promise.resolve([
+            {
+              key: 'UK',
+              children: (): Promise<Components.TreeOutlineUtils.TreeNode[]> => Promise.resolve([
+                {
+                  key: 'LON',
+                  children: (): Promise<Components.TreeOutlineUtils.TreeNode[]> =>
+                      Promise.resolve([{key: '6PS'}, {key: 'CSG'}, {key: 'BEL'}]),
+                },
+              ]),
+            },
+            {
+              key: 'Germany',
+              children: (): Promise<Components.TreeOutlineUtils.TreeNode[]> => Promise.resolve([
+                {key: 'MUC'},
+                {key: 'BER'},
+              ]),
+            },
+          ]),
+        },
+      ]),
+    },
+    {
+      key: 'Products',
+      children: (): Promise<Components.TreeOutlineUtils.TreeNode[]> => Promise.resolve([
+        {
+          key: 'Chrome',
+        },
+        {
+          key: 'YouTube',
+        },
+        {
+          key: 'Drive',
+        },
+        {
+          key: 'Calendar',
+        },
+      ]),
+    },
+  ],
+};
+
+const component = new Components.TreeOutline.TreeOutline();
+component.data = data;
+
+document.getElementById('container')?.appendChild(component);
+document.getElementById('recursively-expand')?.addEventListener('click', () => {
+  component.expandRecursively();
+});
diff --git a/front_end/ui/components/TreeOutline.ts b/front_end/ui/components/TreeOutline.ts
index 22ed1a1ab2..7c8a23a1b6 100644
--- a/front_end/ui/components/TreeOutline.ts
+++ b/front_end/ui/components/TreeOutline.ts
@@ -234,6 +234,8 @@ export class TreeOutline extends HTMLElement {
     });
     const ariaExpandedAttribute = LitHtml.Directives.ifDefined(isExpandableNode(node) ? String(nodeIsExpanded) : undefined);
 
+    const renderedNodeKey = node.renderer ? node.renderer(node.key) : node.key;
+
     return LitHtml.html`
       <li role="treeitem"
         tabindex=${tabIndex}
@@ -248,7 +250,7 @@ export class TreeOutline extends HTMLElement {
         <span class="arrow-and-key-wrapper">
           <span class="arrow-icon" @click=${this.onArrowClick(node)}>
           </span>
-          <span class="tree-node-key" data-node-key>${node.key}</span>
+          <span class="tree-node-key" data-node-key=${node.key}>${renderedNodeKey}</span>
         </span>
         ${childrenToRender}
       </li>
diff --git a/front_end/ui/components/TreeOutlineUtils.ts b/front_end/ui/components/TreeOutlineUtils.ts
index e777a6c1fe..2094871a88 100644
--- a/front_end/ui/components/TreeOutlineUtils.ts
+++ b/front_end/ui/components/TreeOutlineUtils.ts
@@ -6,6 +6,7 @@ import * as LitHtml from '../../third_party/lit-html/lit-html.js';
 
 interface BaseTreeNode {
   key: string;
+  renderer?: (key: string) => LitHtml.TemplateResult;
 }
 
 export interface TreeNodeWithChildren extends BaseTreeNode {
diff --git a/test/unittests/front_end/helpers/DOMHelpers.ts b/test/unittests/front_end/helpers/DOMHelpers.ts
index 7791f6b83a..efb758d63c 100644
--- a/test/unittests/front_end/helpers/DOMHelpers.ts
+++ b/test/unittests/front_end/helpers/DOMHelpers.ts
@@ -189,3 +189,13 @@ export async function doubleRaf() {
 export async function raf() {
   return new Promise(resolve => requestAnimationFrame(resolve));
 }
+
+/**
+  * It's useful to use innerHTML in the tests to have full confidence in the
+  * renderer output, but LitHtml uses comment nodes to split dynamic from
+  * static parts of a template, and we don't want our tests full of noise
+  * from those.
+  */
+export function stripLitHtmlCommentNodes(text: string) {
+  return text.replaceAll('<!---->', '');
+}
diff --git a/test/unittests/front_end/ui/components/DataGrid_test.ts b/test/unittests/front_end/ui/components/DataGrid_test.ts
index 3297a4f69a..9509610bee 100644
--- a/test/unittests/front_end/ui/components/DataGrid_test.ts
+++ b/test/unittests/front_end/ui/components/DataGrid_test.ts
@@ -6,7 +6,7 @@ import * as Platform from '../../../../../front_end/platform/platform.js';
 import * as Coordinator from '../../../../../front_end/render_coordinator/render_coordinator.js';
 import * as LitHtml from '../../../../../front_end/third_party/lit-html/lit-html.js';
 import * as UIComponents from '../../../../../front_end/ui/components/components.js';
-import {assertElement, assertShadowRoot, dispatchClickEvent, dispatchKeyDownEvent, getEventPromise, renderElementIntoDOM} from '../../helpers/DOMHelpers.js';
+import {assertElement, assertShadowRoot, dispatchClickEvent, dispatchKeyDownEvent, getEventPromise, renderElementIntoDOM, stripLitHtmlCommentNodes} from '../../helpers/DOMHelpers.js';
 import {withMutations} from '../../helpers/MutationHelpers.js';
 
 import {assertCurrentFocusedCellIs, emulateUserFocusingCellAt, emulateUserKeyboardNavigation, focusTableCell, getAllRows, getCellByIndexes, getFocusableCell, getHeaderCellForColumnId, getHeaderCells, getValuesOfAllBodyRows, getValuesOfBodyRowByAriaIndex} from './DataGridHelpers.js';
@@ -60,14 +60,6 @@ Object.freeze(columns);
 Object.freeze(columnsWithNoneSortable);
 Object.freeze(rows);
 
-/**
-  * It's useful to use innerHTML in the tests to have full confidence in the
-  * renderer output, but LitHtml uses comment nodes to split dynamic from
-  * static parts of a template, and we don't want our tests full of noise
-  * from those.
-  */
-const stripLitHtmlCommentNodes = (text: string) => text.replaceAll('<!---->', '');
-
 const renderDataGrid = (data: Partial<UIComponents.DataGrid.DataGridData>): UIComponents.DataGrid.DataGrid => {
   const component = new UIComponents.DataGrid.DataGrid();
   component.data = {
diff --git a/test/unittests/front_end/ui/components/TreeOutline_test.ts b/test/unittests/front_end/ui/components/TreeOutline_test.ts
index 9659f61dd6..a631f5ada2 100644
--- a/test/unittests/front_end/ui/components/TreeOutline_test.ts
+++ b/test/unittests/front_end/ui/components/TreeOutline_test.ts
@@ -3,8 +3,9 @@
 // found in the LICENSE file.
 
 import * as Coordinator from '../../../../../front_end/render_coordinator/render_coordinator.js';
+import * as LitHtml from '../../../../../front_end/third_party/lit-html/lit-html.js';
 import * as UIComponents from '../../../../../front_end/ui/components/components.js';
-import {assertElement, assertShadowRoot, dispatchClickEvent, dispatchKeyDownEvent, renderElementIntoDOM} from '../../helpers/DOMHelpers.js';
+import {assertElement, assertShadowRoot, dispatchClickEvent, dispatchKeyDownEvent, renderElementIntoDOM, stripLitHtmlCommentNodes} from '../../helpers/DOMHelpers.js';
 
 const coordinator = Coordinator.RenderCoordinator.RenderCoordinator.instance();
 const {assert} = chai;
@@ -135,8 +136,7 @@ function treeNodeKeyText(node: HTMLLIElement) {
   if (!keyNode) {
     throw new Error('Found tree node without a key within it.');
   }
-  // Trim to remove whitespace that made it into the DOM that we don't care about.
-  return (keyNode.textContent || '').trim();
+  return keyNode.getAttribute('data-node-key') || '';
 }
 
 function getVisibleTreeNodeByText(shadowRoot: ShadowRoot, text: string): HTMLLIElement {
@@ -307,6 +307,36 @@ describe('TreeOutline', () => {
     ]);
   });
 
+  it('allows a node to have a custom renderer', async () => {
+    const tinyTree: UIComponents.TreeOutlineUtils.TreeNode[] = [{
+      key: 'Offices',
+      renderer: key => LitHtml.html`<h2 class="top-node">${key.toUpperCase()}</h2>`,
+      children: () => Promise.resolve([
+        {
+          key: 'EMEA',
+        },
+        {
+          key: 'USA',
+        },
+        {
+          key: 'APAC',
+        },
+      ]),
+    }];
+
+    const {component, shadowRoot} = await renderTreeOutline({
+      tree: tinyTree,
+    });
+
+    await component.expandRecursively(Number.POSITIVE_INFINITY);
+    await coordinator.done();
+    const officeNode = getVisibleTreeNodeByText(shadowRoot, 'Offices');
+    const key = officeNode.querySelector('[data-node-key]');
+    assertElement(key, HTMLElement);
+    const renderedKey = stripLitHtmlCommentNodes(key.innerHTML);
+    assert.strictEqual(renderedKey, '<h2 class="top-node">OFFICES</h2>');
+  });
+
   describe('navigating with keyboard', () => {
     it('defaults to the first root node as active', async () => {
       const {shadowRoot} = await renderTreeOutline({