diff --git a/Lib/profiling/sampling/_flamegraph_assets/flamegraph.css b/Lib/profiling/sampling/_flamegraph_assets/flamegraph.css
index c4da169d15de88..3975130ae10b51 100644
--- a/Lib/profiling/sampling/_flamegraph_assets/flamegraph.css
+++ b/Lib/profiling/sampling/_flamegraph_assets/flamegraph.css
@@ -171,6 +171,7 @@ html, body {
   width: var(--sidebar-width);
   background: var(--bg-secondary);
   border-right: 1px solid var(--border);
+  scrollbar-color: var(--border) var(--bg-secondary);
   display: flex;
   flex-direction: column;
   flex-shrink: 0;
@@ -178,6 +179,19 @@ html, body {
   position: relative;
 }
 
+.sidebar::-webkit-scrollbar {
+  height: 6px;
+}
+
+.sidebar::-webkit-scrollbar-thumb {
+  background: var(--border);
+  border-radius: 3px;
+}
+
+.sidebar::-webkit-scrollbar-thumb:hover {
+  background: var(--text-muted);
+}
+
 .sidebar.collapsed {
   width: var(--sidebar-collapsed) !important;
   transition: width var(--transition-normal);
@@ -748,6 +762,7 @@ body.resizing-sidebar {
   min-width: 0;
   overflow: hidden;
   background: var(--bg-primary);
+  scrollbar-color: var(--border) var(--bg-secondary);
   position: relative;
 }
 
diff --git a/Lib/profiling/sampling/_heatmap_assets/heatmap.css b/Lib/profiling/sampling/_heatmap_assets/heatmap.css
index 8f7f034ba7e596..43594506541728 100644
--- a/Lib/profiling/sampling/_heatmap_assets/heatmap.css
+++ b/Lib/profiling/sampling/_heatmap_assets/heatmap.css
@@ -813,6 +813,10 @@
 }
 
 /* Scrollbar Styling */
+.line-content {
+  scrollbar-color: var(--border) var(--bg-secondary);
+}
+
 .line-content::-webkit-scrollbar {
   height: 6px;
 }
diff --git a/Misc/NEWS.d/next/Library/2026-04-05-10-37-39.gh-issue-142927.B6Gtg9.rst b/Misc/NEWS.d/next/Library/2026-04-05-10-37-39.gh-issue-142927.B6Gtg9.rst
new file mode 100644
index 00000000000000..8ed672595d0476
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2026-04-05-10-37-39.gh-issue-142927.B6Gtg9.rst
@@ -0,0 +1 @@
+Add scrollbar support to Tachyon HTML dark mode