diff --git a/.changeset/perf-buttongroup-has-selector.md b/.changeset/perf-buttongroup-has-selector.md
new file mode 100644
index 00000000000..d9b7e1e546b
--- /dev/null
+++ b/.changeset/perf-buttongroup-has-selector.md
@@ -0,0 +1,5 @@
+---
+'@primer/react': patch
+---
+
+perf(ButtonGroup): Scope :has() selector to direct child for O(1) lookup
diff --git a/packages/react/src/ButtonGroup/ButtonGroup.module.css b/packages/react/src/ButtonGroup/ButtonGroup.module.css
index 7c289b69544..490b13cf49c 100644
--- a/packages/react/src/ButtonGroup/ButtonGroup.module.css
+++ b/packages/react/src/ButtonGroup/ButtonGroup.module.css
@@ -38,7 +38,8 @@
   }
 
   /* this is a workaround until portal based tooltips are fully removed from dotcom */
-  &:has(div:last-child:empty) {
+  /* PERFORMANCE: Scope to direct child for O(1) lookup */
+  &:has(> div:last-child:empty) {
     button,
     a {
       border-radius: var(--borderRadius-medium);