diff --git a/dom/base/nsDOMWindowUtils.cpp b/dom/base/nsDOMWindowUtils.cpp
index c594887e0e2f..38011fb50caa 100644
--- a/dom/base/nsDOMWindowUtils.cpp
+++ b/dom/base/nsDOMWindowUtils.cpp
@@ -1635,13 +1635,13 @@ nsDOMWindowUtils::DisableNonTestMouseEvents(bool aDisable) {
 
 NS_IMETHODIMP
 nsDOMWindowUtils::SuppressEventHandling(bool aSuppress) {
-  nsCOMPtr<Document> doc = GetDocument();
-  NS_ENSURE_TRUE(doc, NS_ERROR_FAILURE);
+  nsCOMPtr<nsPIDOMWindowOuter> window = do_QueryReferent(mWindow);
+  NS_ENSURE_STATE(window);
 
   if (aSuppress) {
-    doc->SuppressEventHandling();
+    window->SuppressEventHandling();
   } else {
-    doc->UnsuppressEventHandlingAndFireEvents(true);
+    window->UnsuppressEventHandling();
   }
 
   return NS_OK;
diff --git a/dom/base/nsGlobalWindowOuter.cpp b/dom/base/nsGlobalWindowOuter.cpp
index a6dbe2d7135e..0532d6bc3ceb 100644
--- a/dom/base/nsGlobalWindowOuter.cpp
+++ b/dom/base/nsGlobalWindowOuter.cpp
@@ -1492,7 +1492,7 @@ void nsGlobalWindowOuter::ShutDown() {
 void nsGlobalWindowOuter::DropOuterWindowDocs() {
   MOZ_ASSERT_IF(mDoc, !mDoc->EventHandlingSuppressed());
   mDoc = nullptr;
-  mSuspendedDoc = nullptr;
+  mSuspendedDocs.Clear();
 }
 
 void nsGlobalWindowOuter::CleanUp() {
@@ -1597,7 +1597,7 @@ NS_IMPL_CYCLE_COLLECTION_TRAVERSE_BEGIN_INTERNAL(nsGlobalWindowOuter)
   NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mArguments)
 
   NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mLocalStorage)
-  NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mSuspendedDoc)
+  NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mSuspendedDocs)
   NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mDocumentPrincipal)
   NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mDocumentStoragePrincipal)
   NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mDocumentPartitionedPrincipal)
@@ -1629,7 +1629,7 @@ NS_IMPL_CYCLE_COLLECTION_UNLINK_BEGIN(nsGlobalWindowOuter)
   NS_IMPL_CYCLE_COLLECTION_UNLINK(mArguments)
 
   NS_IMPL_CYCLE_COLLECTION_UNLINK(mLocalStorage)
-  NS_IMPL_CYCLE_COLLECTION_UNLINK(mSuspendedDoc)
+  NS_IMPL_CYCLE_COLLECTION_UNLINK(mSuspendedDocs)
   NS_IMPL_CYCLE_COLLECTION_UNLINK(mDocumentPrincipal)
   NS_IMPL_CYCLE_COLLECTION_UNLINK(mDocumentStoragePrincipal)
   NS_IMPL_CYCLE_COLLECTION_UNLINK(mDocumentPartitionedPrincipal)
@@ -2157,9 +2157,9 @@ nsresult nsGlobalWindowOuter::SetNewDocument(Document* aDocument,
   mDelayedCloseForPrinting = false;
   mDelayedPrintUntilAfterLoad = false;
 
-  // Take this opportunity to clear mSuspendedDoc. Our old inner window is now
+  // Take this opportunity to clear mSuspendedDocs. Our old inner window is now
   // responsible for unsuspending it.
-  mSuspendedDoc = nullptr;
+  mSuspendedDocs.Clear();
 
 #ifdef DEBUG
   mLastOpenedURI = aDocument->GetDocumentURI();
@@ -6356,6 +6356,44 @@ void nsGlobalWindowOuter::ReallyCloseWindow() {
   CleanUp();
 }
 
+void nsGlobalWindowOuter::SuppressEventHandling() {
+  if (mSuppressEventHandlingDepth == 0) {
+    if (BrowsingContext* bc = GetBrowsingContext()) {
+      bc->PreOrderWalk([&](BrowsingContext* aBC) {
+        if (nsCOMPtr<nsPIDOMWindowOuter> win = aBC->GetDOMWindow()) {
+          if (RefPtr<Document> doc = win->GetExtantDoc()) {
+            mSuspendedDocs.AppendElement(doc);
+            // Note: Document::SuppressEventHandling will also automatically
+            // suppress event handling for any in-process sub-documents.
+            // However, since we need to deal with cases where remote
+            // BrowsingContexts may be interleaved with in-process ones, we
+            // still need to walk the entire tree ourselves. This may be
+            // slightly redundant in some cases, but since event handling
+            // suppressions maintain a count of current blockers, it does not
+            // cause any problems.
+            doc->SuppressEventHandling();
+          }
+        }
+      });
+    }
+  }
+  mSuppressEventHandlingDepth++;
+}
+
+void nsGlobalWindowOuter::UnsuppressEventHandling() {
+  MOZ_ASSERT(mSuppressEventHandlingDepth != 0);
+  mSuppressEventHandlingDepth--;
+
+  if (mSuppressEventHandlingDepth == 0 && mSuspendedDocs.Length()) {
+    RefPtr<Document> currentDoc = GetExtantDoc();
+    bool fireEvent = currentDoc == mSuspendedDocs[0];
+    nsTArray<RefPtr<Document>> suspendedDocs = std::move(mSuspendedDocs);
+    for (const auto& doc : suspendedDocs) {
+      doc->UnsuppressEventHandlingAndFireEvents(fireEvent);
+    }
+  }
+}
+
 nsGlobalWindowOuter* nsGlobalWindowOuter::EnterModalState() {
   // GetInProcessScriptableTop, not GetInProcessTop, so that EnterModalState
   // works properly with <iframe mozbrowser>.
@@ -6406,12 +6444,7 @@ nsGlobalWindowOuter* nsGlobalWindowOuter::EnterModalState() {
   }
 
   if (topWin->mModalStateDepth == 0) {
-    NS_ASSERTION(!topWin->mSuspendedDoc, "Shouldn't have mSuspendedDoc here!");
-
-    topWin->mSuspendedDoc = topDoc;
-    if (topDoc) {
-      topDoc->SuppressEventHandling();
-    }
+    topWin->SuppressEventHandling();
 
     if (nsGlobalWindowInner* inner = topWin->GetCurrentInnerWindowInternal()) {
       inner->Suspend();
@@ -6445,12 +6478,7 @@ void nsGlobalWindowOuter::LeaveModalState() {
       inner->Resume();
     }
 
-    if (mSuspendedDoc) {
-      nsCOMPtr<Document> currentDoc = GetExtantDoc();
-      mSuspendedDoc->UnsuppressEventHandlingAndFireEvents(currentDoc ==
-                                                          mSuspendedDoc);
-      mSuspendedDoc = nullptr;
-    }
+    UnsuppressEventHandling();
   }
 
   // Remember the time of the last dialog quit.
@@ -7711,6 +7739,7 @@ mozilla::dom::DocGroup* nsPIDOMWindowOuter::GetDocGroup() const {
 nsPIDOMWindowOuter::nsPIDOMWindowOuter(uint64_t aWindowID)
     : mFrameElement(nullptr),
       mModalStateDepth(0),
+      mSuppressEventHandlingDepth(0),
       mIsBackground(false),
       mMediaSuspend(StaticPrefs::media_block_autoplay_until_in_foreground()
                         ? nsISuspendedTypes::SUSPENDED_BLOCK
diff --git a/dom/base/nsGlobalWindowOuter.h b/dom/base/nsGlobalWindowOuter.h
index 6b55b7da87a7..a5073e3c9c53 100644
--- a/dom/base/nsGlobalWindowOuter.h
+++ b/dom/base/nsGlobalWindowOuter.h
@@ -328,6 +328,9 @@ class nsGlobalWindowOuter final : public mozilla::dom::EventTarget,
   // Outer windows only.
   virtual void EnsureSizeAndPositionUpToDate() override;
 
+  virtual void SuppressEventHandling() override;
+  virtual void UnsuppressEventHandling() override;
+
   MOZ_CAN_RUN_SCRIPT_BOUNDARY virtual nsGlobalWindowOuter* EnterModalState()
       override;
   virtual void LeaveModalState() override;
@@ -1128,10 +1131,10 @@ class nsGlobalWindowOuter final : public mozilla::dom::EventTarget,
 
   // It's useful when we get matched EnterModalState/LeaveModalState calls, in
   // which case the outer window is responsible for unsuspending events on the
-  // document. If we don't (for example, if the outer window is closed before
-  // the LeaveModalState call), then the inner window whose mDoc is our
-  // mSuspendedDoc is responsible for unsuspending it.
-  RefPtr<Document> mSuspendedDoc;
+  // documents. If we don't (for example, if the outer window is closed before
+  // the LeaveModalState call), then the inner window whose mDoc is in our
+  // mSuspendedDocs is responsible for unsuspending.
+  nsTArray<RefPtr<Document>> mSuspendedDocs;
 
   // This is the CC generation the last time we called CanSkip.
   uint32_t mCanSkipCCGeneration;
diff --git a/dom/base/nsPIDOMWindow.h b/dom/base/nsPIDOMWindow.h
index 40322a6e99b1..ca1b1137dfe8 100644
--- a/dom/base/nsPIDOMWindow.h
+++ b/dom/base/nsPIDOMWindow.h
@@ -910,6 +910,13 @@ class nsPIDOMWindowOuter : public mozIDOMWindowProxy {
    */
   virtual void EnsureSizeAndPositionUpToDate() = 0;
 
+  /**
+   * Suppresses/unsuppresses user initiated event handling in window's document
+   * and all in-process descendant documents.
+   */
+  virtual void SuppressEventHandling() = 0;
+  virtual void UnsuppressEventHandling() = 0;
+
   /**
    * Callback for notifying a window about a modal dialog being
    * opened/closed with the window as a parent.
@@ -1124,6 +1131,8 @@ class nsPIDOMWindowOuter : public mozIDOMWindowProxy {
 
   uint32_t mModalStateDepth;
 
+  uint32_t mSuppressEventHandlingDepth;
+
   // Tracks whether our docshell is active.  If it is, mIsBackground
   // is false.  Too bad we have so many different concepts of
   // "active".
diff --git a/dom/base/test/file_suppressed_events_top.html b/dom/base/test/file_suppressed_events_top.html
new file mode 100644
index 000000000000..ca031abb7057
--- /dev/null
+++ b/dom/base/test/file_suppressed_events_top.html
@@ -0,0 +1,79 @@
+<!DOCTYPE HTML>
+<html>
+<head>
+<title>Test event suppression</title>
+<script src="/tests/SimpleTest/SimpleTest.js"></script>
+<script src="/tests/SimpleTest/EventUtils.js"></script>
+<script src="/tests/SimpleTest/paint_listener.js"></script>
+<script src="/tests/gfx/layers/apz/test/mochitest/apz_test_utils.js"></script>
+<link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css"/>
+</head>
+<body>
+<div>Top</div>
+<script type="application/javascript">
+
+function waitForMessage(aMsg, aCallback) {
+  window.addEventListener("message", function handler(e) {
+    if (e.data != aMsg) {
+      return;
+    }
+
+    info(`received: ${e.data}`);
+    window.removeEventListener("message", handler);
+    if (aCallback) {
+      aCallback(e);
+    }
+  });
+}
+
+function waitForClickEvent(aElement, aWindow) {
+  return new Promise((aResolve) => {
+    aElement.addEventListener("click", aResolve, { once: true });
+    synthesizeMouseAtCenter(aElement, { type: "mousedown" }, aWindow);
+    synthesizeMouseAtCenter(aElement, { type: "mouseup" }, aWindow);
+  });
+}
+
+waitForMessage("ready", async function(e) {
+  await waitUntilApzStable();
+
+  let innerWin = e.source;
+  let innerDiv = innerWin.document.querySelector("div");
+
+  let eventCount = 0;
+  innerDiv.addEventListener("mousemove", function() {
+    eventCount++;
+  });
+
+  // Test that event handling is suppressed.
+  let utils = SpecialPowers.getDOMWindowUtils(window);
+  utils.suppressEventHandling(true);
+  const TOTAL = 100;
+  for (let i = 0; i < TOTAL; i++) {
+    synthesizeMouseAtCenter(innerDiv, { type: "mousemove" }, innerWin);
+  }
+  utils.suppressEventHandling(false);
+
+  // Wait for click event to ensure we have received all mousemove events.
+  await waitForClickEvent(innerDiv, innerWin);
+  opener.info(`eventCount: ${eventCount}`);
+  opener.ok(eventCount < TOTAL, "event should be suspressed");
+
+  // Test that event handling is not suppressed.
+  eventCount = 0;
+  for (let i = 0; i < TOTAL; i++) {
+    synthesizeMouseAtCenter(innerDiv, { type: "mousemove" }, innerWin);
+  }
+
+  // Wait for click event to ensure we have received all mousemove events.
+  await waitForClickEvent(innerDiv, innerWin);
+  opener.info(`eventCount: ${eventCount}`);
+  opener.is(eventCount, TOTAL, "event should not be suspressed");
+
+  opener.postMessage("done", "*");
+});
+
+</script>
+<iframe src="http://example.org/tests/dom/base/test/file_suppressed_events_middle.html"></iframe>
+</body>
+</html>
diff --git a/dom/base/test/file_suppressed_events_top_modalstate.html b/dom/base/test/file_suppressed_events_top_modalstate.html
new file mode 100644
index 000000000000..e20938bb2886
--- /dev/null
+++ b/dom/base/test/file_suppressed_events_top_modalstate.html
@@ -0,0 +1,79 @@
+<!DOCTYPE HTML>
+<html>
+<head>
+<title>Test event suppression</title>
+<script src="/tests/SimpleTest/SimpleTest.js"></script>
+<script src="/tests/SimpleTest/EventUtils.js"></script>
+<script src="/tests/SimpleTest/paint_listener.js"></script>
+<script src="/tests/gfx/layers/apz/test/mochitest/apz_test_utils.js"></script>
+<link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css"/>
+</head>
+<body>
+<div>Top</div>
+<script type="application/javascript">
+
+function waitForMessage(aMsg, aCallback) {
+  window.addEventListener("message", function handler(e) {
+    if (e.data != aMsg) {
+      return;
+    }
+
+    info(`received: ${e.data}`);
+    window.removeEventListener("message", handler);
+    if (aCallback) {
+      aCallback(e);
+    }
+  });
+}
+
+function waitForClickEvent(aElement, aWindow) {
+  return new Promise((aResolve) => {
+    aElement.addEventListener("click", aResolve, { once: true });
+    synthesizeMouseAtCenter(aElement, { type: "mousedown" }, aWindow);
+    synthesizeMouseAtCenter(aElement, { type: "mouseup" }, aWindow);
+  });
+}
+
+waitForMessage("ready", async function(e) {
+  await waitUntilApzStable();
+
+  let innerWin = e.source;
+  let innerDiv = innerWin.document.querySelector("div");
+
+  let eventCount = 0;
+  innerDiv.addEventListener("mousemove", function() {
+    eventCount++;
+  });
+
+  // Test that event handling is suppressed.
+  let utils = SpecialPowers.getDOMWindowUtils(window);
+  utils.enterModalState();
+  const TOTAL = 100;
+  for (let i = 0; i < TOTAL; i++) {
+    synthesizeMouseAtCenter(innerDiv, { type: "mousemove" }, innerWin);
+  }
+  utils.leaveModalState();
+
+  // Wait for click event to ensure we have received all mousemove events.
+  await waitForClickEvent(innerDiv, innerWin);
+  opener.info(`eventCount: ${eventCount}`);
+  opener.ok(eventCount < TOTAL, "event should be suspressed");
+
+  // Test that event handling is not suppressed.
+  eventCount = 0;
+  for (let i = 0; i < TOTAL; i++) {
+    synthesizeMouseAtCenter(innerDiv, { type: "mousemove" }, innerWin);
+  }
+
+  // Wait for click event to ensure we have received all mousemove events.
+  await waitForClickEvent(innerDiv, innerWin);
+  opener.info(`eventCount: ${eventCount}`);
+  opener.is(eventCount, TOTAL, "event should not be suspressed");
+
+  opener.postMessage("done", "*");
+});
+
+</script>
+<iframe src="http://example.org/tests/dom/base/test/file_suppressed_events_middle.html"></iframe>
+</body>
+</html>
diff --git a/dom/base/test/mochitest.ini b/dom/base/test/mochitest.ini
index 80c10ea38a14..413fba39ff08 100644
--- a/dom/base/test/mochitest.ini
+++ b/dom/base/test/mochitest.ini
@@ -778,6 +778,8 @@ support-files =
 skip-if = os == "android"
 support-files =
   file_suppressed_events_top_xhr.html
+  file_suppressed_events_top_modalstate.html
+  file_suppressed_events_top.html
   file_suppressed_events_middle.html
   file_suppressed_events_inner.html
   !/gfx/layers/apz/test/mochitest/apz_test_utils.js
diff --git a/dom/base/test/test_suppressed_events_nested_iframe.html b/dom/base/test/test_suppressed_events_nested_iframe.html
index b9865ec00fe7..1d31c7c5d60b 100644
--- a/dom/base/test/test_suppressed_events_nested_iframe.html
+++ b/dom/base/test/test_suppressed_events_nested_iframe.html
@@ -43,6 +43,28 @@ add_task(async function test_sync_xhr() {
   w.close();
 });
 
+add_task(async function test_modalstate() {
+  await SpecialPowers.pushPrefEnv({"set": [
+    ["test.events.async.enabled", false],
+    ["dom.events.coalesce.mousemove", false],
+  ]});
+
+  let w = window.open("file_suppressed_events_top_modalstate.html");
+  await waitForMessage("done");
+  w.close();
+});
+
+add_task(async function test_suppress_event_handling() {
+  await SpecialPowers.pushPrefEnv({"set": [
+    ["test.events.async.enabled", false],
+    ["dom.events.coalesce.mousemove", false],
+  ]});
+
+  let w = window.open("file_suppressed_events_top.html");
+  await waitForMessage("done");
+  w.close();
+});
+
 </script>
 </pre>
 </body>