diff --git a/third_party/blink/renderer/modules/push_messaging/push_manager.cc b/third_party/blink/renderer/modules/push_messaging/push_manager.cc
index bae0c24044f6ee..c4c16b2aaca249 100644
--- a/third_party/blink/renderer/modules/push_messaging/push_manager.cc
+++ b/third_party/blink/renderer/modules/push_messaging/push_manager.cc
@@ -14,6 +14,7 @@
 #include "third_party/blink/renderer/core/execution_context/execution_context.h"
 #include "third_party/blink/renderer/core/frame/frame.h"
 #include "third_party/blink/renderer/core/frame/local_frame.h"
+#include "third_party/blink/renderer/core/inspector/console_message.h"
 #include "third_party/blink/renderer/modules/push_messaging/push_error.h"
 #include "third_party/blink/renderer/modules/push_messaging/push_messaging_bridge.h"
 #include "third_party/blink/renderer/modules/push_messaging/push_messaging_client.h"
@@ -66,6 +67,16 @@ ScriptPromise PushManager::subscribe(
   if (exception_state.HadException())
     return ScriptPromise();
 
+  if (!options->IsApplicationServerKeyVapid()) {
+    ExecutionContext::From(script_state)
+        ->AddConsoleMessage(ConsoleMessage::Create(
+            mojom::ConsoleMessageSource::kJavaScript,
+            mojom::ConsoleMessageLevel::kWarning,
+            "The provided application server key is not a VAPID key. Only "
+            "VAPID keys will be supported in the future. For more information "
+            "check https://crbug.com/979235."));
+  }
+
   auto* resolver = MakeGarbageCollected<ScriptPromiseResolver>(script_state);
   ScriptPromise promise = resolver->Promise();
 
diff --git a/third_party/blink/renderer/modules/push_messaging/push_subscription_options.cc b/third_party/blink/renderer/modules/push_messaging/push_subscription_options.cc
index 2a670c72809321..1db027ac0bc4db 100644
--- a/third_party/blink/renderer/modules/push_messaging/push_subscription_options.cc
+++ b/third_party/blink/renderer/modules/push_messaging/push_subscription_options.cc
@@ -98,6 +98,13 @@ PushSubscriptionOptions::PushSubscriptionOptions(
           application_server_key.data(),
           SafeCast<unsigned>(application_server_key.size()))) {}
 
+bool PushSubscriptionOptions::IsApplicationServerKeyVapid() const {
+  if (!application_server_key_)
+    return false;
+  return application_server_key_->ByteLength() == 65 &&
+         static_cast<uint8_t*>(application_server_key_->Data())[0] == 0x04;
+}
+
 void PushSubscriptionOptions::Trace(blink::Visitor* visitor) {
   visitor->Trace(application_server_key_);
   ScriptWrappable::Trace(visitor);
diff --git a/third_party/blink/renderer/modules/push_messaging/push_subscription_options.h b/third_party/blink/renderer/modules/push_messaging/push_subscription_options.h
index e0dc22a98fc38a..3907c3643d9603 100644
--- a/third_party/blink/renderer/modules/push_messaging/push_subscription_options.h
+++ b/third_party/blink/renderer/modules/push_messaging/push_subscription_options.h
@@ -44,6 +44,9 @@ class PushSubscriptionOptions final : public ScriptWrappable {
     return application_server_key_;
   }
 
+  // Whether the application server key follows the VAPID protocol.
+  bool IsApplicationServerKeyVapid() const;
+
   void Trace(blink::Visitor* visitor) override;
 
  private: