diff --git a/Libraries/LibWeb/HTML/HTMLDialogElement.cpp b/Libraries/LibWeb/HTML/HTMLDialogElement.cpp
index ea838cd0dee..33352026d13 100644
--- a/Libraries/LibWeb/HTML/HTMLDialogElement.cpp
+++ b/Libraries/LibWeb/HTML/HTMLDialogElement.cpp
@@ -43,6 +43,7 @@ void HTMLDialogElement::visit_edges(JS::Cell::Visitor& visitor)
 
     visitor.visit(m_close_watcher);
     visitor.visit(m_request_close_source_element);
+    visitor.visit(m_previously_focused_element);
 }
 
 void HTMLDialogElement::removed_from(Node* old_parent, Node& old_root)
@@ -142,7 +143,9 @@ WebIDL::ExceptionOr<void> HTMLDialogElement::show()
 
     // 9. Set the dialog close watcher with this.
     set_close_watcher();
-    // FIXME: 10. Set this's previously focused element to the focused element.
+
+    // 10. Set this's previously focused element to the focused element.
+    m_previously_focused_element = document().focused_area();
 
     // 11. Let document be this's node document.
     auto document = m_document;
@@ -358,7 +361,8 @@ void HTMLDialogElement::close_the_dialog(Optional<String> result, GC::Ptr<DOM::E
     if (m_is_modal)
         document().request_an_element_to_be_remove_from_the_top_layer(*this);
 
-    // FIXME: 7. Let wasModal be the value of subject's is modal flag.
+    // 7. Let wasModal be the value of subject's is modal flag.
+    auto was_modal = m_is_modal;
 
     // 8. Set the is modal flag of subject to false.
     set_is_modal(false);
@@ -376,11 +380,21 @@ void HTMLDialogElement::close_the_dialog(Optional<String> result, GC::Ptr<DOM::E
     // 12. Set subject's request close source element to null.
     m_request_close_source_element = nullptr;
 
-    // FIXME: 13. If subject's previously focused element is not null, then:
-    //           1. Let element be subject's previously focused element.
-    //           2. Set subject's previously focused element to null.
-    //           3. If subject's node document's focused area of the document's DOM anchor is a shadow-including inclusive descendant of subject,
-    //              or wasModal is true, then run the focusing steps for element; the viewport should not be scrolled by doing this step.
+    // 13. If subject's previously focused element is not null, then:
+    if (m_previously_focused_element) {
+        // 1. Let element be subject's previously focused element.
+        auto element = m_previously_focused_element;
+
+        // 2. Set subject's previously focused element to null.
+        m_previously_focused_element = nullptr;
+
+        // 3. If subject's node document's focused area of the document's DOM anchor is a shadow-including inclusive descendant of subject,
+        //    or wasModal is true, then run the focusing steps for element; the viewport should not be scrolled by doing this step.
+        auto focused_element = document().focused_area();
+        auto is_focus_within_dialog = focused_element && focused_element->is_shadow_including_inclusive_descendant_of(*this);
+        if (is_focus_within_dialog || was_modal)
+            run_focusing_steps(element);
+    }
 
     // 14. Queue an element task on the user interaction task source given the subject element to fire an event named close at subject.
     queue_an_element_task(HTML::Task::Source::UserInteraction, [this] {
diff --git a/Libraries/LibWeb/HTML/HTMLDialogElement.h b/Libraries/LibWeb/HTML/HTMLDialogElement.h
index a7e794fc2af..e49b04e3fb0 100644
--- a/Libraries/LibWeb/HTML/HTMLDialogElement.h
+++ b/Libraries/LibWeb/HTML/HTMLDialogElement.h
@@ -72,6 +72,9 @@ private:
 
     // https://html.spec.whatwg.org/multipage/interactive-elements.html#dialog-toggle-task-tracker
     Optional<ToggleTaskTracker> m_dialog_toggle_task_tracker;
+
+    // https://html.spec.whatwg.org/multipage/interactive-elements.html#previously-focused-element
+    GC::Ptr<Node> m_previously_focused_element;
 };
 
 }
diff --git a/Tests/LibWeb/Text/expected/wpt-import/html/semantics/interactive-elements/the-dialog-element/dialog-focus-previous-outside.txt b/Tests/LibWeb/Text/expected/wpt-import/html/semantics/interactive-elements/the-dialog-element/dialog-focus-previous-outside.txt
new file mode 100644
index 00000000000..9fd4d26fc98
--- /dev/null
+++ b/Tests/LibWeb/Text/expected/wpt-import/html/semantics/interactive-elements/the-dialog-element/dialog-focus-previous-outside.txt
@@ -0,0 +1,11 @@
+Harness status: OK
+
+Found 5 tests
+
+3 Pass
+2 Fail
+Pass	Focus should not be restored if the currently focused element is not inside the dialog.
+Pass	Focus restore should not occur when the focused element is in a shadowroot outside of the dialog.
+Pass	Focus restore should occur when the focused element is in a shadowroot inside the dialog.
+Fail	Focus restore should occur when the focused element is slotted into a dialog.
+Fail	Focus restore should always occur for modal dialogs.
\ No newline at end of file
diff --git a/Tests/LibWeb/Text/input/wpt-import/html/semantics/interactive-elements/the-dialog-element/dialog-focus-previous-outside.html b/Tests/LibWeb/Text/input/wpt-import/html/semantics/interactive-elements/the-dialog-element/dialog-focus-previous-outside.html
new file mode 100644
index 00000000000..a35df88e31d
--- /dev/null
+++ b/Tests/LibWeb/Text/input/wpt-import/html/semantics/interactive-elements/the-dialog-element/dialog-focus-previous-outside.html
@@ -0,0 +1,82 @@
+<!DOCTYPE html>
+<link rel=author href="mailto:jarhar@chromium.org">
+<link rel=help href="https://github.com/whatwg/html/issues/8904">
+<script src="../../../../resources/testharness.js"></script>
+<script src="../../../../resources/testharnessreport.js"></script>
+
+<button id=b1>button 1</button>
+<button id=b2>button 2</button>
+<div id=host>
+  <template shadowrootmode=open>
+    <button>button in shadowroot outside dialog</button>
+  </template>
+</div>
+<dialog id=mydialog>
+  <button id=b3>button in dialog</button>
+  <div id=dialoghost>
+    <template shadowrootmode=open>
+      <button>button in shadowroot in dialog</button>
+    </template>
+  </div>
+</dialog>
+
+<div id=host2>
+  <template shadowrootmode=open>
+    <dialog>
+      <slot></slot>
+    </dialog>
+  </template>
+  <button id=host2button>button</button>
+</div>
+
+<dialog id=mydialog2>hello world</dialog>
+
+<script>
+test(() => {
+  b1.focus();
+  mydialog.show();
+  b2.focus();
+  mydialog.close();
+  assert_equals(document.activeElement, b2);
+}, 'Focus should not be restored if the currently focused element is not inside the dialog.');
+
+test(() => {
+  const shadowbutton = host.shadowRoot.querySelector('button');
+  b2.focus();
+  mydialog.show();
+  shadowbutton.focus();
+  mydialog.close();
+  assert_equals(document.activeElement, host, 'document.activeElement should point at the shadow host.');
+  assert_equals(host.shadowRoot.activeElement, shadowbutton, 'The button in the shadowroot should remain focused.');
+}, 'Focus restore should not occur when the focused element is in a shadowroot outside of the dialog.');
+
+test(() => {
+  const shadowbutton = dialoghost.shadowRoot.querySelector('button');
+  b2.focus();
+  mydialog.show();
+  shadowbutton.focus();
+  mydialog.close();
+  assert_equals(document.activeElement, b2);
+}, 'Focus restore should occur when the focused element is in a shadowroot inside the dialog.');
+
+test(() => {
+  const dialog = host2.shadowRoot.querySelector('dialog');
+  b2.focus();
+  dialog.show();
+  host2button.focus();
+  dialog.close();
+  assert_equals(document.activeElement, b2);
+}, 'Focus restore should occur when the focused element is slotted into a dialog.');
+
+test(() => {
+  b1.focus();
+  const dialog = document.getElementById('mydialog2');
+  dialog.showModal();
+  dialog.blur();
+  assert_equals(document.activeElement, document.body,
+    'Focus should return to the body when calling dialog.blur().');
+  dialog.close();
+  assert_equals(document.activeElement, b1,
+    'Focus should be restored to the previously focused element.');
+}, 'Focus restore should always occur for modal dialogs.');
+</script>