diff --git a/.changeset/ten-gifts-own.md b/.changeset/ten-gifts-own.md
new file mode 100644
index 00000000000..1d743aecde9
--- /dev/null
+++ b/.changeset/ten-gifts-own.md
@@ -0,0 +1,5 @@
+---
+"@primer/react": patch
+---
+
+SelectPanel: Fix focus and selection styles for Windows high contrast themes (behind feature flag `primer_react_select_panel_with_modern_action_list`)
diff --git a/.playwright/snapshots/components/SelectPanel.test.ts-snapshots/SelectPanel-Default-forced-colors-dark-modern-action-list--true-linux.png b/.playwright/snapshots/components/SelectPanel.test.ts-snapshots/SelectPanel-Default-forced-colors-dark-modern-action-list--true-linux.png
new file mode 100644
index 00000000000..25d8a0cf18b
Binary files /dev/null and b/.playwright/snapshots/components/SelectPanel.test.ts-snapshots/SelectPanel-Default-forced-colors-dark-modern-action-list--true-linux.png differ
diff --git a/.playwright/snapshots/components/SelectPanel.test.ts-snapshots/SelectPanel-Default-forced-colors-light-modern-action-list--true-linux.png b/.playwright/snapshots/components/SelectPanel.test.ts-snapshots/SelectPanel-Default-forced-colors-light-modern-action-list--true-linux.png
new file mode 100644
index 00000000000..2c12a24a104
Binary files /dev/null and b/.playwright/snapshots/components/SelectPanel.test.ts-snapshots/SelectPanel-Default-forced-colors-light-modern-action-list--true-linux.png differ
diff --git a/e2e/components/SelectPanel.test.ts b/e2e/components/SelectPanel.test.ts
index e4f61864b17..bc6614cee1e 100644
--- a/e2e/components/SelectPanel.test.ts
+++ b/e2e/components/SelectPanel.test.ts
@@ -60,4 +60,27 @@ test.describe('SelectPanel', () => {
       await expect(page).toHaveNoViolations()
     })
   }
+
+  test(`Default @vrt forced-colors .modern-action-list--true`, async ({page}) => {
+    await visit(page, {
+      id: 'components-selectpanel--default',
+      globals: {featureFlags: {primer_react_select_panel_with_modern_action_list: true}},
+    })
+
+    // Open select panel
+    await page.keyboard.press('Tab')
+    await page.keyboard.press('Enter')
+
+    // windows high contrast mode: light
+    await page.emulateMedia({forcedColors: 'active', colorScheme: 'light'})
+    expect(await page.screenshot({animations: 'disabled'})).toMatchSnapshot(
+      `SelectPanel-Default-forced-colors-light-modern-action-list--true.png`,
+    )
+
+    // windows high contrast mode: dark
+    await page.emulateMedia({forcedColors: 'active', colorScheme: 'dark'})
+    expect(await page.screenshot({animations: 'disabled'})).toMatchSnapshot(
+      `SelectPanel-Default-forced-colors-dark-modern-action-list--true.png`,
+    )
+  })
 })
diff --git a/packages/react/src/ActionList/Item.tsx b/packages/react/src/ActionList/Item.tsx
index 8e3da1de68a..629e1d3b5c1 100644
--- a/packages/react/src/ActionList/Item.tsx
+++ b/packages/react/src/ActionList/Item.tsx
@@ -196,7 +196,7 @@ export const Item = React.forwardRef<HTMLLIElement, ActionListItemProps>(
       marginY: 'unset',
 
       '@media (forced-colors: active)': {
-        ':focus, &:focus-visible, > a.focus-visible': {
+        ':focus, &:focus-visible, > a.focus-visible, &[data-is-active-descendant]': {
           // Support for Windows high contrast https://sarahmhigley.com/writing/whcm-quick-tips
           outline: 'solid 1px transparent !important',
         },
diff --git a/packages/react/src/ActionList/Selection.tsx b/packages/react/src/ActionList/Selection.tsx
index e5b9c3e1617..4d705e2faf4 100644
--- a/packages/react/src/ActionList/Selection.tsx
+++ b/packages/react/src/ActionList/Selection.tsx
@@ -97,6 +97,11 @@ export const Selection: React.FC<React.PropsWithChildren<SelectionProps>> = ({se
             '@keyframes checkmarkIn': checkmarkIn,
             '@keyframes checkmarkOut': checkmarkOut,
           },
+          '@media (forced-colors: active)': {
+            // Support for Windows high contrast https://sarahmhigley.com/writing/whcm-quick-tips
+            // background-color will be overriden but border-width is a workaround
+            borderWidth: selected ? '8px' : '1px',
+          },
         }}
         data-component="ActionList.Checkbox"
       />
diff --git a/packages/react/src/NavList/__snapshots__/NavList.test.tsx.snap b/packages/react/src/NavList/__snapshots__/NavList.test.tsx.snap
index 76ad7525713..339503e6711 100644
--- a/packages/react/src/NavList/__snapshots__/NavList.test.tsx.snap
+++ b/packages/react/src/NavList/__snapshots__/NavList.test.tsx.snap
@@ -304,7 +304,8 @@ exports[`NavList renders a simple list 1`] = `
 @media (forced-colors:active) {
   .c2:focus,
   .c2:focus-visible,
-  .c2 > a.focus-visible {
+  .c2 > a.focus-visible,
+  .c2[data-is-active-descendant] {
     outline: solid 1px transparent !important;
   }
 }
@@ -333,7 +334,8 @@ exports[`NavList renders a simple list 1`] = `
 @media (forced-colors:active) {
   .c7:focus,
   .c7:focus-visible,
-  .c7 > a.focus-visible {
+  .c7 > a.focus-visible,
+  .c7[data-is-active-descendant] {
     outline: solid 1px transparent !important;
   }
 }
@@ -794,7 +796,8 @@ exports[`NavList renders with groups 1`] = `
 @media (forced-colors:active) {
   .c6:focus,
   .c6:focus-visible,
-  .c6 > a.focus-visible {
+  .c6 > a.focus-visible,
+  .c6[data-is-active-descendant] {
     outline: solid 1px transparent !important;
   }
 }
@@ -823,7 +826,8 @@ exports[`NavList renders with groups 1`] = `
 @media (forced-colors:active) {
   .c11:focus,
   .c11:focus-visible,
-  .c11 > a.focus-visible {
+  .c11 > a.focus-visible,
+  .c11[data-is-active-descendant] {
     outline: solid 1px transparent !important;
   }
 }
@@ -1313,7 +1317,8 @@ exports[`NavList.Item with NavList.SubNav does not have active styles if SubNav
 @media (forced-colors:active) {
   .c11:focus,
   .c11:focus-visible,
-  .c11 > a.focus-visible {
+  .c11 > a.focus-visible,
+  .c11[data-is-active-descendant] {
     outline: solid 1px transparent !important;
   }
 }
@@ -1342,7 +1347,8 @@ exports[`NavList.Item with NavList.SubNav does not have active styles if SubNav
 @media (forced-colors:active) {
   .c4:focus,
   .c4:focus-visible,
-  .c4 > a.focus-visible {
+  .c4 > a.focus-visible,
+  .c4[data-is-active-descendant] {
     outline: solid 1px transparent !important;
   }
 }
@@ -1837,7 +1843,8 @@ exports[`NavList.Item with NavList.SubNav has active styles if SubNav contains t
 @media (forced-colors:active) {
   .c11:focus,
   .c11:focus-visible,
-  .c11 > a.focus-visible {
+  .c11 > a.focus-visible,
+  .c11[data-is-active-descendant] {
     outline: solid 1px transparent !important;
   }
 }
@@ -1874,7 +1881,8 @@ exports[`NavList.Item with NavList.SubNav has active styles if SubNav contains t
 @media (forced-colors:active) {
   .c4:focus,
   .c4:focus-visible,
-  .c4 > a.focus-visible {
+  .c4 > a.focus-visible,
+  .c4[data-is-active-descendant] {
     outline: solid 1px transparent !important;
   }
 }
diff --git a/packages/react/src/__tests__/__snapshots__/Autocomplete.test.tsx.snap b/packages/react/src/__tests__/__snapshots__/Autocomplete.test.tsx.snap
index 5317c8136b8..92301474008 100644
--- a/packages/react/src/__tests__/__snapshots__/Autocomplete.test.tsx.snap
+++ b/packages/react/src/__tests__/__snapshots__/Autocomplete.test.tsx.snap
@@ -527,6 +527,14 @@ exports[`snapshots renders a menu that contains an item to add to the menu 1`] =
 
 }
 
+@media (forced-colors:active) {
+
+}
+
+@media (forced-colors:active) {
+
+}
+
 @media (hover:hover) and (pointer:fine) {
 
 }
@@ -812,10 +820,21 @@ exports[`snapshots renders a menu that contains an item to add to the menu 1`] =
   --divider-color: transparent;
 }
 
+@media (forced-colors:active) {
+  .c6 {
+    border-width: 1px;
+  }
+}
+
+@media (forced-colors:active) {
+
+}
+
 @media (forced-colors:active) {
   .c3:focus,
   .c3:focus-visible,
-  .c3 > a.focus-visible {
+  .c3 > a.focus-visible,
+  .c3[data-is-active-descendant] {
     outline: solid 1px transparent !important;
   }
 }
@@ -1359,6 +1378,10 @@ exports[`snapshots renders a multiselect input 1`] = `
 
 }
 
+@media (forced-colors:active) {
+
+}
+
 @media (hover:hover) and (pointer:fine) {
 
 }
@@ -1595,10 +1618,17 @@ exports[`snapshots renders a multiselect input 1`] = `
   border-radius: 6px;
 }
 
+@media (forced-colors:active) {
+  .c5 {
+    border-width: 1px;
+  }
+}
+
 @media (forced-colors:active) {
   .c3:focus,
   .c3:focus-visible,
-  .c3 > a.focus-visible {
+  .c3 > a.focus-visible,
+  .c3[data-is-active-descendant] {
     outline: solid 1px transparent !important;
   }
 }
@@ -2077,6 +2107,14 @@ exports[`snapshots renders a multiselect input with selected menu items 1`] = `
 
 }
 
+@media (forced-colors:active) {
+
+}
+
+@media (forced-colors:active) {
+
+}
+
 @media (hover:hover) and (pointer:fine) {
 
 }
@@ -2456,10 +2494,23 @@ exports[`snapshots renders a multiselect input with selected menu items 1`] = `
   border-radius: 6px;
 }
 
+@media (forced-colors:active) {
+  .c5 {
+    border-width: 8px;
+  }
+}
+
+@media (forced-colors:active) {
+  .c9 {
+    border-width: 1px;
+  }
+}
+
 @media (forced-colors:active) {
   .c3:focus,
   .c3:focus-visible,
-  .c3 > a.focus-visible {
+  .c3 > a.focus-visible,
+  .c3[data-is-active-descendant] {
     outline: solid 1px transparent !important;
   }
 }
@@ -2488,7 +2539,8 @@ exports[`snapshots renders a multiselect input with selected menu items 1`] = `
 @media (forced-colors:active) {
   .c8:focus,
   .c8:focus-visible,
-  .c8 > a.focus-visible {
+  .c8 > a.focus-visible,
+  .c8[data-is-active-descendant] {
     outline: solid 1px transparent !important;
   }
 }
@@ -3168,7 +3220,8 @@ exports[`snapshots renders a single select input 1`] = `
 @media (forced-colors:active) {
   .c3:focus,
   .c3:focus-visible,
-  .c3 > a.focus-visible {
+  .c3 > a.focus-visible,
+  .c3[data-is-active-descendant] {
     outline: solid 1px transparent !important;
   }
 }
@@ -3654,7 +3707,8 @@ exports[`snapshots renders with a custom text input component 1`] = `
 @media (forced-colors:active) {
   .c3:focus,
   .c3:focus-visible,
-  .c3 > a.focus-visible {
+  .c3 > a.focus-visible,
+  .c3[data-is-active-descendant] {
     outline: solid 1px transparent !important;
   }
 }