diff --git a/.changeset/light-beds-stare.md b/.changeset/light-beds-stare.md
new file mode 100644
index 00000000000..fefb2d4319a
--- /dev/null
+++ b/.changeset/light-beds-stare.md
@@ -0,0 +1,5 @@
+---
+"@primer/react": patch
+---
+
+Overlay: Fix position for fullscreen overlay on narrow screens
diff --git a/packages/react/src/Overlay/Overlay.module.css b/packages/react/src/Overlay/Overlay.module.css
index 5aab9024d0a..de584ec2aa0 100644
--- a/packages/react/src/Overlay/Overlay.module.css
+++ b/packages/react/src/Overlay/Overlay.module.css
@@ -158,6 +158,7 @@
   }
 
   &:where([data-variant='fullscreen']) {
+    position: fixed;
     top: 0;
     left: 0;
     width: 100vw;
diff --git a/packages/react/src/Overlay/Overlay.tsx b/packages/react/src/Overlay/Overlay.tsx
index 519be0d24f4..f7d32cc24af 100644
--- a/packages/react/src/Overlay/Overlay.tsx
+++ b/packages/react/src/Overlay/Overlay.tsx
@@ -104,6 +104,7 @@ const StyledOverlay = toggleStyledComponent(
     }
 
     &:where([data-variant='fullscreen']) {
+      position: fixed;
       top: 0;
       left: 0;
       width: 100vw;
diff --git a/packages/react/src/__tests__/__snapshots__/AnchoredOverlay.test.tsx.snap b/packages/react/src/__tests__/__snapshots__/AnchoredOverlay.test.tsx.snap
index ce4d66ef15a..99f22fc126d 100644
--- a/packages/react/src/__tests__/__snapshots__/AnchoredOverlay.test.tsx.snap
+++ b/packages/react/src/__tests__/__snapshots__/AnchoredOverlay.test.tsx.snap
@@ -31,6 +31,7 @@ exports[`AnchoredOverlay should render consistently when open 1`] = `
 }
 
 .c1:where([data-variant='fullscreen']) {
+  position: fixed;
   top: 0;
   left: 0;
   width: 100vw;