diff --git a/src/components/stack-chart/Canvas.tsx b/src/components/stack-chart/Canvas.tsx
index a30950153b..50661e63cb 100644
--- a/src/components/stack-chart/Canvas.tsx
+++ b/src/components/stack-chart/Canvas.tsx
@@ -78,6 +78,7 @@ type OwnProps = {
   readonly displayStackType: boolean;
   readonly useStackChartSameWidths: boolean;
   readonly timelineUnit: TimelineUnit;
+  readonly searchStringsRegExp: RegExp | null;
 };
 
 type Props = Readonly<
@@ -183,6 +184,7 @@ class StackChartCanvasImpl extends React.PureComponent<Props> {
       getMarker,
       marginLeft,
       useStackChartSameWidths,
+      searchStringsRegExp,
       viewport: {
         containerWidth,
         containerHeight,
@@ -359,6 +361,26 @@ class StackChartCanvasImpl extends React.PureComponent<Props> {
 
     const callNodeTable = callNodeInfo.getCallNodeTable();
 
+    // Pre-compute which call nodes match the search string so we can dim
+    // non-matching nodes when a search is active.
+    let searchMatchedCallNodes: Set<IndexIntoCallNodeTable> | null = null;
+    if (searchStringsRegExp) {
+      searchMatchedCallNodes = new Set();
+      for (
+        let callNodeIndex = 0;
+        callNodeIndex < callNodeTable.length;
+        callNodeIndex++
+      ) {
+        const funcIndex = callNodeTable.func[callNodeIndex];
+        const funcNameIndex = thread.funcTable.name[funcIndex];
+        const funcName = thread.stringTable.getString(funcNameIndex);
+        searchStringsRegExp.lastIndex = 0;
+        if (searchStringsRegExp.test(funcName)) {
+          searchMatchedCallNodes.add(callNodeIndex);
+        }
+      }
+    }
+
     // Only draw the stack frames that are vertically within view.
     for (let depth = startDepth; depth < endDepth; depth++) {
       // Get the timing information for a row of stack frames.
@@ -480,8 +502,10 @@ class StackChartCanvasImpl extends React.PureComponent<Props> {
 
         // Look up information about this stack frame.
         let text, category, isSelected;
+        let currentCallNodeIndex: IndexIntoCallNodeTable | null = null;
         if ('callNode' in stackTiming && stackTiming.callNode) {
           const callNodeIndex = stackTiming.callNode[i];
+          currentCallNodeIndex = callNodeIndex;
           const funcIndex = callNodeTable.func[callNodeIndex];
           const funcNameIndex = thread.funcTable.name[funcIndex];
           text = thread.stringTable.getString(funcNameIndex);
@@ -510,6 +534,16 @@ class StackChartCanvasImpl extends React.PureComponent<Props> {
         const colorStyles = mapCategoryColorNameToStackChartStyles(
           category.color
         );
+
+        // When a search is active, dim boxes that do not match.
+        const isDimmed =
+          searchMatchedCallNodes !== null &&
+          currentCallNodeIndex !== null &&
+          !searchMatchedCallNodes.has(currentCallNodeIndex);
+        if (isDimmed) {
+          ctx.globalAlpha = 0.5;
+        }
+
         // Draw the box.
         fastFillStyle.set(
           isHovered || isSelected
@@ -550,6 +584,11 @@ class StackChartCanvasImpl extends React.PureComponent<Props> {
             ctx.fillText(fittedText, textX, intY + textDevicePixelsOffsetTop);
           }
         }
+
+        // Reset dimming after drawing.
+        if (isDimmed) {
+          ctx.globalAlpha = 1;
+        }
       }
     }
 
diff --git a/src/components/stack-chart/index.tsx b/src/components/stack-chart/index.tsx
index ba98f87a9b..1fdc46658d 100644
--- a/src/components/stack-chart/index.tsx
+++ b/src/components/stack-chart/index.tsx
@@ -23,6 +23,7 @@ import {
   getStackChartSameWidths,
   getShowUserTimings,
   getSelectedThreadsKey,
+  getSearchStringsAsRegExp,
 } from 'firefox-profiler/selectors/url-state';
 import type { SameWidthsIndexToTimestampMap } from 'firefox-profiler/profile-logic/stack-timing';
 import { selectedThreadSelectors } from '../../selectors/per-thread';
@@ -87,6 +88,7 @@ type StateProps = {
   readonly hasFilteredCtssSamples: boolean;
   readonly useStackChartSameWidths: boolean;
   readonly timelineUnit: TimelineUnit;
+  readonly searchStringsRegExp: RegExp | null;
 };
 
 type DispatchProps = {
@@ -244,6 +246,7 @@ class StackChartImpl extends React.PureComponent<Props> {
       hasFilteredCtssSamples,
       useStackChartSameWidths,
       timelineUnit,
+      searchStringsRegExp,
     } = this.props;
 
     const maxViewportHeight = combinedTimingRows.length * STACK_FRAME_HEIGHT;
@@ -304,6 +307,7 @@ class StackChartImpl extends React.PureComponent<Props> {
                   displayStackType: displayStackType,
                   useStackChartSameWidths,
                   timelineUnit,
+                  searchStringsRegExp,
                 }}
               />
             </div>
@@ -347,6 +351,7 @@ export const StackChart = explicitConnect<{}, StateProps, DispatchProps>({
         selectedThreadSelectors.getHasFilteredCtssSamples(state),
       useStackChartSameWidths: getStackChartSameWidths(state),
       timelineUnit: getProfileTimelineUnit(state),
+      searchStringsRegExp: getSearchStringsAsRegExp(state),
     };
   },
   mapDispatchToProps: {
diff --git a/src/test/components/StackChart.test.tsx b/src/test/components/StackChart.test.tsx
index e8a2769361..e407b9de0b 100644
--- a/src/test/components/StackChart.test.tsx
+++ b/src/test/components/StackChart.test.tsx
@@ -33,6 +33,7 @@ import {
   changeImplementationFilter,
   changeCallTreeSummaryStrategy,
   updatePreviewSelection,
+  changeCallTreeSearchString,
 } from '../../actions/profile-view';
 import { changeSelectedTab } from '../../actions/app';
 import { selectedThreadSelectors } from '../../selectors/per-thread';
@@ -271,6 +272,56 @@ describe('StackChart', function () {
     expect(drawnFrames).not.toContain('Z');
   });
 
+  it('dims non-matching boxes when searching', function () {
+    const { dispatch, flushRafCalls } = setupSamples();
+    flushDrawLog();
+
+    // Dispatch a search string that matches some function names.
+    act(() => {
+      dispatch(changeCallTreeSearchString('B'));
+    });
+    flushRafCalls();
+
+    const drawCalls = flushDrawLog();
+
+    // Non-matching boxes should be drawn with reduced globalAlpha.
+    const dimCalls = drawCalls.filter(
+      ([fn, value]) => fn === 'set globalAlpha' && value === 0.5
+    );
+    expect(dimCalls.length).toBeGreaterThan(0);
+  });
+
+  it('does not dim boxes that match the search string', function () {
+    // Use a single-node call stack so there is exactly one box.
+    const { dispatch, flushRafCalls } = setupSamples(`
+      A[cat:DOM]
+    `);
+    flushDrawLog();
+
+    // Search for "A" — the only node matches, so nothing should be dimmed.
+    act(() => {
+      dispatch(changeCallTreeSearchString('A'));
+    });
+    flushRafCalls();
+
+    const drawCalls = flushDrawLog();
+    const dimCalls = drawCalls.filter(
+      ([fn, value]) => fn === 'set globalAlpha' && value < 1
+    );
+    expect(dimCalls).toHaveLength(0);
+  });
+
+  it('does not dim any boxes when there is no search string', function () {
+    setupSamples();
+    const drawCalls = flushDrawLog();
+
+    // No dimming should be applied without a search.
+    const dimCalls = drawCalls.filter(
+      ([fn, value]) => fn === 'set globalAlpha' && value < 1
+    );
+    expect(dimCalls).toHaveLength(0);
+  });
+
   describe('EmptyReasons', () => {
     it('shows reasons when a profile has no samples', () => {
       const profile = getEmptyProfile();
diff --git a/src/test/fixtures/mocks/canvas-context.ts b/src/test/fixtures/mocks/canvas-context.ts
index 27eef057fb..6742557cd0 100644
--- a/src/test/fixtures/mocks/canvas-context.ts
+++ b/src/test/fixtures/mocks/canvas-context.ts
@@ -35,6 +35,7 @@ export type SetFillStyleOperation = ['set fillStyle', string];
 export type FillRectOperation = ['fillRect', number, number, number, number];
 export type ClearRectOperation = ['clearRect', number, number, number, number];
 export type FillTextOperation = ['fillText', string];
+export type SetGlobalAlphaOperation = ['set globalAlpha', number];
 
 export type DrawOperation =
   | BeginPathOperation
@@ -44,7 +45,8 @@ export type DrawOperation =
   | SetFillStyleOperation
   | FillRectOperation
   | ClearRectOperation
-  | FillTextOperation;
+  | FillTextOperation
+  | SetGlobalAlphaOperation;
 
 export function flushDrawLog(): DrawOperation[] {
   return (window as any).__flushDrawLog();