diff --git a/browser/installer/windows/msix/AppxManifest.xml.in b/browser/installer/windows/msix/AppxManifest.xml.in
index 845db766f4d9..74b14226189d 100644
--- a/browser/installer/windows/msix/AppxManifest.xml.in
+++ b/browser/installer/windows/msix/AppxManifest.xml.in
@@ -85,6 +85,20 @@
             <uap:Logo>Assets\Document44x44.png</uap:Logo>
           </uap3:Protocol>
         </uap3:Extension>
+        <!-- COM registrations for the notification server. -->
+        <com:Extension Category="windows.comServer">
+          <com:ComServer>
+            <com:SurrogateServer DisplayName="NotificationServer"
+                                 AppId="@MOZ_INOTIFICATIONACTIVATION_CLSID@">
+              <com:Class Id="@MOZ_INOTIFICATIONACTIVATION_CLSID@"
+                         Path="VFS\ProgramFiles\@APPX_INSTDIR@\notificationserver.dll"
+                         ThreadingModel="Both" />
+            </com:SurrogateServer>
+          </com:ComServer>
+        </com:Extension>
+        <desktop:Extension Category="windows.toastNotificationActivation">
+          <desktop:ToastNotificationActivation ToastActivatorCLSID="@MOZ_INOTIFICATIONACTIVATION_CLSID@" />
+        </desktop:Extension>
       </Extensions>
     </Application>
   </Applications>
diff --git a/python/mozbuild/mozbuild/repackaging/msix.py b/python/mozbuild/mozbuild/repackaging/msix.py
index 1baa06455157..b6b279c13549 100644
--- a/python/mozbuild/mozbuild/repackaging/msix.py
+++ b/python/mozbuild/mozbuild/repackaging/msix.py
@@ -631,6 +631,8 @@ def repackage_msix(
         "APPX_VERSION": version,
         "MOZ_APP_DISPLAYNAME": displayname,
         "MOZ_APP_NAME": app_name,
+        # Keep synchronized with `toolkit\mozapps\notificationserver\NotificationComServer.cpp`.
+        "MOZ_INOTIFICATIONACTIVATION_CLSID": "916f9b5d-b5b2-4d36-b047-03c7a52f81c8",
     }
     defines.update(brandingUuids)
 
diff --git a/toolkit/mozapps/notificationserver/NotificationComServer.cpp b/toolkit/mozapps/notificationserver/NotificationComServer.cpp
index 35a8aa46d31a..184b55be44cc 100644
--- a/toolkit/mozapps/notificationserver/NotificationComServer.cpp
+++ b/toolkit/mozapps/notificationserver/NotificationComServer.cpp
@@ -7,6 +7,8 @@
 #include <filesystem>
 #include <string>
 
+#include "mozilla/WinHeaderOnlyUtils.h"
+
 #include "NotificationFactory.h"
 
 using namespace std::filesystem;
@@ -41,10 +43,23 @@ bool PopulateDllPath(HINSTANCE dllInstance) {
 // requested we verify the CLSID's InprocServer registry entry matches this
 // DLL's path.
 bool CheckRuntimeClsid(REFCLSID rclsid) {
+  // MSIX Notification COM Server registration is isolated to the package and is
+  // identical across installs/channels.
+  if (mozilla::HasPackageIdentity()) {
+    // Keep synchronized with `python\mozbuild\mozbuild\repackaging\msix.py`.
+    constexpr CLSID MOZ_INOTIFICATIONACTIVATION_CLSID = {
+        0x916f9b5d,
+        0xb5b2,
+        0x4d36,
+        {0xb0, 0x47, 0x03, 0xc7, 0xa5, 0x2f, 0x81, 0xc8}};
+
+    return IsEqualCLSID(rclsid, MOZ_INOTIFICATIONACTIVATION_CLSID);
+  }
+
   std::wstring clsid_str;
   {
     wchar_t* raw_clsid_str;
-    if (StringFromCLSID(rclsid, &raw_clsid_str) == S_OK) {
+    if (SUCCEEDED(StringFromCLSID(rclsid, &raw_clsid_str))) {
       clsid_str += raw_clsid_str;
       CoTaskMemFree(raw_clsid_str);
     } else {