diff --git a/change/@fluentui-react-combobox-dropdown-high-contrast-border.json b/change/@fluentui-react-combobox-dropdown-high-contrast-border.json
new file mode 100644
index 00000000000000..518089d84f8bdf
--- /dev/null
+++ b/change/@fluentui-react-combobox-dropdown-high-contrast-border.json
@@ -0,0 +1,7 @@
+{
+  "type": "patch",
+  "comment": "fix: render filled Dropdown boundaries in high contrast themes",
+  "packageName": "@fluentui/react-combobox",
+  "email": "bernardo.sunderhus@gmail.com",
+  "dependentChangeType": "patch"
+}
diff --git a/packages/react-components/react-combobox/library/src/components/Dropdown/useDropdownStyles.styles.ts b/packages/react-components/react-combobox/library/src/components/Dropdown/useDropdownStyles.styles.ts
index 244ef16f28b09c..3b2f3b57a8e366 100644
--- a/packages/react-components/react-combobox/library/src/components/Dropdown/useDropdownStyles.styles.ts
+++ b/packages/react-components/react-combobox/library/src/components/Dropdown/useDropdownStyles.styles.ts
@@ -171,11 +171,11 @@ const useStyles = makeStyles({
   },
   'filled-lighter': {
     backgroundColor: tokens.colorNeutralBackground1,
-    border: `${tokens.strokeWidthThin} solid transparent`,
+    border: `${tokens.strokeWidthThin} solid ${tokens.colorTransparentStroke}`,
   },
   'filled-darker': {
     backgroundColor: tokens.colorNeutralBackground3,
-    border: `${tokens.strokeWidthThin} solid transparent`,
+    border: `${tokens.strokeWidthThin} solid ${tokens.colorTransparentStroke}`,
   },
   invalid: {
     ':not(:focus-within),:hover:not(:focus-within)': {