diff --git a/src/components/file-upload/_file-upload.scss b/src/components/file-upload/_file-upload.scss
index acfd3540c3..780fff3c28 100644
--- a/src/components/file-upload/_file-upload.scss
+++ b/src/components/file-upload/_file-upload.scss
@@ -34,6 +34,24 @@
         border: 4px solid $govuk-input-border-colour;
       }
     }
+
+    // Set "focus-within" to fix https://bugzilla.mozilla.org/show_bug.cgi?id=1430196
+    // so that component receives focus in Firefox.
+    // This can't be set together with `:focus` as all versions of IE fail
+    // to recognise `focus-within` and don't set any styles from the block
+    // when it's a selector.
+    &:focus-within {
+      margin-right: -$spacing-unit;
+      margin-left: -$spacing-unit;
+      padding-right: $spacing-unit;
+      padding-left: $spacing-unit;
+
+      // Emulate `govuk-focusable` mixin styles for this component in FF
+      outline: $govuk-focus-width solid $govuk-focus-colour;
+      outline-offset: 0;
+
+      box-shadow: inset 0 0 0 4px $govuk-input-border-colour;
+    }
   }
 
   .govuk-file-upload--error {