diff --git a/accessible/mac/MOXAccessibleProtocol.h b/accessible/mac/MOXAccessibleProtocol.h
index 07ea53f27f2d..05f450c27385 100644
--- a/accessible/mac/MOXAccessibleProtocol.h
+++ b/accessible/mac/MOXAccessibleProtocol.h
@@ -124,6 +124,9 @@
 // AXRequired
 - (NSNumber* _Nullable)moxRequired;
 
+// AXElementBusy
+- (NSNumber* _Nullable)moxElementBusy;
+
 // AXDOMIdentifier
 - (NSString* _Nullable)moxDOMIdentifier;
 
diff --git a/accessible/mac/MOXWebAreaAccessible.h b/accessible/mac/MOXWebAreaAccessible.h
index f46e562700b4..1ef11af50c09 100644
--- a/accessible/mac/MOXWebAreaAccessible.h
+++ b/accessible/mac/MOXWebAreaAccessible.h
@@ -38,6 +38,9 @@ using namespace mozilla::a11y;
 // override
 - (BOOL)moxBlockSelector:(SEL)selector;
 
+// override
+- (void)moxPostNotification:(NSString*)notification;
+
 // override
 - (void)handleAccessibleEvent:(uint32_t)eventType;
 
diff --git a/accessible/mac/MOXWebAreaAccessible.mm b/accessible/mac/MOXWebAreaAccessible.mm
index 74504df1cf6e..b91732325c91 100644
--- a/accessible/mac/MOXWebAreaAccessible.mm
+++ b/accessible/mac/MOXWebAreaAccessible.mm
@@ -223,9 +223,23 @@ using namespace mozilla::a11y;
     return YES;
   }
 
+  if (selector == @selector(moxElementBusy)) {
+    // Don't confuse aria-busy with a document's busy state.
+    return YES;
+  }
+
   return [super moxBlockSelector:selector];
 }
 
+- (void)moxPostNotification:(NSString*)notification {
+  if (![notification isEqualToString:@"AXElementBusyChanged"]) {
+    // Suppress AXElementBusyChanged since it uses gecko's BUSY state
+    // to tell VoiceOver about aria-busy changes. We use that state
+    // differently in documents.
+    [super moxPostNotification:notification];
+  }
+}
+
 - (id)rootGroup {
   NSArray* children = [super moxUnignoredChildren];
   if (mRole != roles::APPLICATION && [children count] == 1 &&
diff --git a/accessible/mac/mozAccessible.h b/accessible/mac/mozAccessible.h
index 5c188e194b83..4f5b7b09dfd7 100644
--- a/accessible/mac/mozAccessible.h
+++ b/accessible/mac/mozAccessible.h
@@ -208,6 +208,9 @@ inline mozAccessible* GetNativeFromGeckoAccessible(
 // override
 - (NSNumber*)moxRequired;
 
+// override
+- (NSNumber*)moxElementBusy;
+
 // override
 - (id)moxEditableAncestor;
 
diff --git a/accessible/mac/mozAccessible.mm b/accessible/mac/mozAccessible.mm
index 705cda3131cb..717fa7cb6730 100644
--- a/accessible/mac/mozAccessible.mm
+++ b/accessible/mac/mozAccessible.mm
@@ -111,7 +111,7 @@ using namespace mozilla::a11y;
 static const uint64_t kCachedStates =
     states::CHECKED | states::PRESSED | states::MIXED | states::EXPANDED |
     states::CURRENT | states::SELECTED | states::TRAVERSED | states::LINKED |
-    states::HASPOPUP;
+    states::HASPOPUP | states::BUSY;
 static const uint64_t kCacheInitialized = ((uint64_t)0x1) << 63;
 
 - (uint64_t)state {
@@ -143,19 +143,20 @@ static const uint64_t kCacheInitialized = ((uint64_t)0x1) << 63;
 }
 
 - (void)stateChanged:(uint64_t)state isEnabled:(BOOL)enabled {
-  if ((state & kCachedStates) == 0) {
-    return;
+  if ((state & kCachedStates) != 0) {
+    if (!(mCachedState & kCacheInitialized)) {
+      [self state];
+    } else {
+      if (enabled) {
+        mCachedState |= state;
+      } else {
+        mCachedState &= ~state;
+      }
+    }
   }
 
-  if (!(mCachedState & kCacheInitialized)) {
-    [self state];
-    return;
-  }
-
-  if (enabled) {
-    mCachedState |= state;
-  } else {
-    mCachedState &= ~state;
+  if (state == states::BUSY) {
+    [self moxPostNotification:@"AXElementBusyChanged"];
   }
 }
 
@@ -789,6 +790,10 @@ struct RoleDescrComparator {
   return @([self stateWithMask:states::REQUIRED] != 0);
 }
 
+- (NSNumber*)moxElementBusy {
+  return @([self stateWithMask:states::BUSY] != 0);
+}
+
 - (mozAccessible*)topWebArea {
   AccessibleOrProxy doc = [self geckoDocument];
   while (!doc.IsNull()) {
diff --git a/accessible/tests/browser/mac/browser.ini b/accessible/tests/browser/mac/browser.ini
index ed634797d5ff..81258af48b14 100644
--- a/accessible/tests/browser/mac/browser.ini
+++ b/accessible/tests/browser/mac/browser.ini
@@ -46,3 +46,4 @@ skip-if = os == 'mac' && debug # Bug 1664577
 [browser_menulist.js]
 [browser_rich_listbox.js]
 [browser_live_regions.js]
+[browser_aria_busy.js]
diff --git a/accessible/tests/browser/mac/browser_aria_busy.js b/accessible/tests/browser/mac/browser_aria_busy.js
new file mode 100644
index 000000000000..e75d334e295b
--- /dev/null
+++ b/accessible/tests/browser/mac/browser_aria_busy.js
@@ -0,0 +1,44 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+"use strict";
+
+/* import-globals-from ../../mochitest/role.js */
+/* import-globals-from ../../mochitest/states.js */
+loadScripts(
+  { name: "role.js", dir: MOCHITESTS_DIR },
+  { name: "states.js", dir: MOCHITESTS_DIR }
+);
+
+/**
+ * Test aria-busy
+ */
+addAccessibleTask(
+  `<div id="section" role="group">Hello</div>`,
+  async (browser, accDoc) => {
+    let section = getNativeInterface(accDoc, "section");
+
+    ok(!section.getAttributeValue("AXElementBusy"), "section is not busy");
+
+    let busyChanged = waitForMacEvent("AXElementBusyChanged", "section");
+    await SpecialPowers.spawn(browser, [], () => {
+      content.document
+        .getElementById("section")
+        .setAttribute("aria-busy", "true");
+    });
+    await busyChanged;
+
+    ok(section.getAttributeValue("AXElementBusy"), "section is busy");
+
+    busyChanged = waitForMacEvent("AXElementBusyChanged", "section");
+    await SpecialPowers.spawn(browser, [], () => {
+      content.document
+        .getElementById("section")
+        .setAttribute("aria-busy", "false");
+    });
+    await busyChanged;
+
+    ok(!section.getAttributeValue("AXElementBusy"), "section is not busy");
+  }
+);