diff --git a/src/Symfony/Bundle/FrameworkBundle/CHANGELOG.md b/src/Symfony/Bundle/FrameworkBundle/CHANGELOG.md
index 2dd441182d15d..098f168e3b8df 100644
--- a/src/Symfony/Bundle/FrameworkBundle/CHANGELOG.md
+++ b/src/Symfony/Bundle/FrameworkBundle/CHANGELOG.md
@@ -7,6 +7,12 @@ CHANGELOG
  * Not passing the project directory to the constructor of the `AssetsInstallCommand` is deprecated. This argument will
    be mandatory in 5.0.
 
+ * [BC Break] When using Messenger, the default transport changed from
+   using Symfony's serializer service to use `PhpSerializer`, which uses
+   PHP's native `serialize()` and `unserialize()` functions. To use the
+   original serialization method, set the `framework.messenger.serializer.id`
+   config option to `messenger.transport.symfony_serializer`.
+
 4.2.0
 -----
 
diff --git a/src/Symfony/Bundle/FrameworkBundle/DependencyInjection/Configuration.php b/src/Symfony/Bundle/FrameworkBundle/DependencyInjection/Configuration.php
index 1a8d6fb461991..b1849afde8360 100644
--- a/src/Symfony/Bundle/FrameworkBundle/DependencyInjection/Configuration.php
+++ b/src/Symfony/Bundle/FrameworkBundle/DependencyInjection/Configuration.php
@@ -1060,7 +1060,7 @@ function ($a) {
                                 })
                             ->end()
                             ->children()
-                                ->scalarNode('id')->defaultValue(!class_exists(FullStack::class) && class_exists(Serializer::class) ? 'messenger.transport.symfony_serializer' : null)->end()
+                                ->scalarNode('id')->defaultValue('messenger.transport.native_php_serializer')->end()
                                 ->scalarNode('format')->defaultValue('json')->end()
                                 ->arrayNode('context')
                                     ->normalizeKeys(false)
diff --git a/src/Symfony/Bundle/FrameworkBundle/DependencyInjection/FrameworkExtension.php b/src/Symfony/Bundle/FrameworkBundle/DependencyInjection/FrameworkExtension.php
index 679064b8cc043..8a1ec7bb5cd49 100644
--- a/src/Symfony/Bundle/FrameworkBundle/DependencyInjection/FrameworkExtension.php
+++ b/src/Symfony/Bundle/FrameworkBundle/DependencyInjection/FrameworkExtension.php
@@ -1529,7 +1529,7 @@ private function registerMessengerConfiguration(array $config, ContainerBuilder
         } else {
             if ('messenger.transport.symfony_serializer' === $config['serializer']['id']) {
                 if (!$this->isConfigEnabled($container, $serializerConfig)) {
-                    throw new LogicException('The default Messenger serializer cannot be enabled as the Serializer support is not available. Try enabling it or running "composer require symfony/serializer-pack".');
+                    throw new LogicException('The Messenger serializer cannot be enabled as the Serializer support is not available. Try enabling it or running "composer require symfony/serializer-pack".');
                 }
 
                 $container->getDefinition('messenger.transport.symfony_serializer')
diff --git a/src/Symfony/Bundle/FrameworkBundle/Resources/config/messenger.xml b/src/Symfony/Bundle/FrameworkBundle/Resources/config/messenger.xml
index 9d8a0ff74dd42..92ec3b555e4d3 100644
--- a/src/Symfony/Bundle/FrameworkBundle/Resources/config/messenger.xml
+++ b/src/Symfony/Bundle/FrameworkBundle/Resources/config/messenger.xml
@@ -24,6 +24,8 @@
         </service>
         <service id="Symfony\Component\Messenger\Transport\Serialization\SerializerInterface" alias="messenger.transport.serializer" />
 
+        <service id="messenger.transport.native_php_serializer" class="Symfony\Component\Messenger\Transport\Serialization\PhpSerializer" />
+
         <!-- Middleware -->
         <service id="messenger.middleware.handle_message" class="Symfony\Component\Messenger\Middleware\HandleMessageMiddleware" abstract="true">
             <argument /> <!-- Bus handler resolver -->
diff --git a/src/Symfony/Bundle/FrameworkBundle/Tests/DependencyInjection/ConfigurationTest.php b/src/Symfony/Bundle/FrameworkBundle/Tests/DependencyInjection/ConfigurationTest.php
index 453ccf449dd11..d8acb04909809 100644
--- a/src/Symfony/Bundle/FrameworkBundle/Tests/DependencyInjection/ConfigurationTest.php
+++ b/src/Symfony/Bundle/FrameworkBundle/Tests/DependencyInjection/ConfigurationTest.php
@@ -19,7 +19,6 @@
 use Symfony\Component\Config\Definition\Processor;
 use Symfony\Component\Lock\Store\SemaphoreStore;
 use Symfony\Component\Messenger\MessageBusInterface;
-use Symfony\Component\Serializer\Serializer;
 
 class ConfigurationTest extends TestCase
 {
@@ -295,7 +294,7 @@ class_exists(SemaphoreStore::class) && SemaphoreStore::isSupported() ? 'semaphor
                 'routing' => [],
                 'transports' => [],
                 'serializer' => [
-                    'id' => !class_exists(FullStack::class) && class_exists(Serializer::class) ? 'messenger.transport.symfony_serializer' : null,
+                    'id' => 'messenger.transport.native_php_serializer',
                     'format' => 'json',
                     'context' => [],
                 ],
diff --git a/src/Symfony/Bundle/FrameworkBundle/Tests/DependencyInjection/FrameworkExtensionTest.php b/src/Symfony/Bundle/FrameworkBundle/Tests/DependencyInjection/FrameworkExtensionTest.php
index 862786c9b8b80..6d3563d0781c9 100644
--- a/src/Symfony/Bundle/FrameworkBundle/Tests/DependencyInjection/FrameworkExtensionTest.php
+++ b/src/Symfony/Bundle/FrameworkBundle/Tests/DependencyInjection/FrameworkExtensionTest.php
@@ -660,7 +660,7 @@ public function testMessengerRouting()
 
     /**
      * @expectedException \Symfony\Component\DependencyInjection\Exception\LogicException
-     * @expectedExceptionMessage The default Messenger serializer cannot be enabled as the Serializer support is not available. Try enabling it or running "composer require symfony/serializer-pack".
+     * @expectedExceptionMessage The Messenger serializer cannot be enabled as the Serializer support is not available. Try enabling it or running "composer require symfony/serializer-pack".
      */
     public function testMessengerTransportConfigurationWithoutSerializer()
     {
diff --git a/src/Symfony/Component/Messenger/CHANGELOG.md b/src/Symfony/Component/Messenger/CHANGELOG.md
index eb1268e25e818..ff901be210f10 100644
--- a/src/Symfony/Component/Messenger/CHANGELOG.md
+++ b/src/Symfony/Component/Messenger/CHANGELOG.md
@@ -1,6 +1,16 @@
 CHANGELOG
 =========
 
+4.3.0
+-----
+
+ * Added `PhpSerializer` which uses PHP's native `serialize()` and
+   `unserialize()` to serialize messages to a transport
+
+ * [BC BREAK] If no serializer were passed, the default serializer
+   changed from `Serializer` to `PhpSerializer` inside `AmqpReceiver`,
+   `AmqpSender`, `AmqpTransport` and `AmqpTransportFactory`.
+
 4.2.0
 -----
 
diff --git a/src/Symfony/Component/Messenger/Tests/Transport/Serialization/PhpSerializerTest.php b/src/Symfony/Component/Messenger/Tests/Transport/Serialization/PhpSerializerTest.php
new file mode 100644
index 0000000000000..d3f1da25e456c
--- /dev/null
+++ b/src/Symfony/Component/Messenger/Tests/Transport/Serialization/PhpSerializerTest.php
@@ -0,0 +1,29 @@
+<?php
+
+/*
+ * This file is part of the Symfony package.
+ *
+ * (c) Fabien Potencier <fabien@symfony.com>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace Symfony\Component\Messenger\Tests\Transport\Serialization;
+
+use PHPUnit\Framework\TestCase;
+use Symfony\Component\Messenger\Envelope;
+use Symfony\Component\Messenger\Tests\Fixtures\DummyMessage;
+use Symfony\Component\Messenger\Transport\Serialization\PhpSerializer;
+
+class PhpSerializerTest extends TestCase
+{
+    public function testEncodedIsDecodable()
+    {
+        $serializer = new PhpSerializer();
+
+        $envelope = new Envelope(new DummyMessage('Hello'));
+
+        $this->assertEquals($envelope, $serializer->decode($serializer->encode($envelope)));
+    }
+}
diff --git a/src/Symfony/Component/Messenger/Transport/AmqpExt/AmqpReceiver.php b/src/Symfony/Component/Messenger/Transport/AmqpExt/AmqpReceiver.php
index 7ed1fae405819..fdd81cac543ab 100644
--- a/src/Symfony/Component/Messenger/Transport/AmqpExt/AmqpReceiver.php
+++ b/src/Symfony/Component/Messenger/Transport/AmqpExt/AmqpReceiver.php
@@ -13,7 +13,7 @@
 
 use Symfony\Component\Messenger\Transport\AmqpExt\Exception\RejectMessageExceptionInterface;
 use Symfony\Component\Messenger\Transport\Receiver\ReceiverInterface;
-use Symfony\Component\Messenger\Transport\Serialization\Serializer;
+use Symfony\Component\Messenger\Transport\Serialization\PhpSerializer;
 use Symfony\Component\Messenger\Transport\Serialization\SerializerInterface;
 
 /**
@@ -32,7 +32,7 @@ class AmqpReceiver implements ReceiverInterface
     public function __construct(Connection $connection, SerializerInterface $serializer = null)
     {
         $this->connection = $connection;
-        $this->serializer = $serializer ?? Serializer::create();
+        $this->serializer = $serializer ?? new PhpSerializer();
     }
 
     /**
diff --git a/src/Symfony/Component/Messenger/Transport/AmqpExt/AmqpSender.php b/src/Symfony/Component/Messenger/Transport/AmqpExt/AmqpSender.php
index 88b99ebb063a4..74ab0dfaa92aa 100644
--- a/src/Symfony/Component/Messenger/Transport/AmqpExt/AmqpSender.php
+++ b/src/Symfony/Component/Messenger/Transport/AmqpExt/AmqpSender.php
@@ -13,7 +13,7 @@
 
 use Symfony\Component\Messenger\Envelope;
 use Symfony\Component\Messenger\Transport\Sender\SenderInterface;
-use Symfony\Component\Messenger\Transport\Serialization\Serializer;
+use Symfony\Component\Messenger\Transport\Serialization\PhpSerializer;
 use Symfony\Component\Messenger\Transport\Serialization\SerializerInterface;
 
 /**
@@ -31,7 +31,7 @@ class AmqpSender implements SenderInterface
     public function __construct(Connection $connection, SerializerInterface $serializer = null)
     {
         $this->connection = $connection;
-        $this->serializer = $serializer ?? Serializer::create();
+        $this->serializer = $serializer ?? new PhpSerializer();
     }
 
     /**
diff --git a/src/Symfony/Component/Messenger/Transport/AmqpExt/AmqpTransport.php b/src/Symfony/Component/Messenger/Transport/AmqpExt/AmqpTransport.php
index 8e27fb90d866e..36967c8459dca 100644
--- a/src/Symfony/Component/Messenger/Transport/AmqpExt/AmqpTransport.php
+++ b/src/Symfony/Component/Messenger/Transport/AmqpExt/AmqpTransport.php
@@ -12,7 +12,7 @@
 namespace Symfony\Component\Messenger\Transport\AmqpExt;
 
 use Symfony\Component\Messenger\Envelope;
-use Symfony\Component\Messenger\Transport\Serialization\Serializer;
+use Symfony\Component\Messenger\Transport\Serialization\PhpSerializer;
 use Symfony\Component\Messenger\Transport\Serialization\SerializerInterface;
 use Symfony\Component\Messenger\Transport\TransportInterface;
 
@@ -31,7 +31,7 @@ class AmqpTransport implements TransportInterface
     public function __construct(Connection $connection, SerializerInterface $serializer = null)
     {
         $this->connection = $connection;
-        $this->serializer = $serializer ?? Serializer::create();
+        $this->serializer = $serializer ?? new PhpSerializer();
     }
 
     /**
diff --git a/src/Symfony/Component/Messenger/Transport/AmqpExt/AmqpTransportFactory.php b/src/Symfony/Component/Messenger/Transport/AmqpExt/AmqpTransportFactory.php
index b958726ea55c8..477aaf1c551aa 100644
--- a/src/Symfony/Component/Messenger/Transport/AmqpExt/AmqpTransportFactory.php
+++ b/src/Symfony/Component/Messenger/Transport/AmqpExt/AmqpTransportFactory.php
@@ -11,7 +11,7 @@
 
 namespace Symfony\Component\Messenger\Transport\AmqpExt;
 
-use Symfony\Component\Messenger\Transport\Serialization\Serializer;
+use Symfony\Component\Messenger\Transport\Serialization\PhpSerializer;
 use Symfony\Component\Messenger\Transport\Serialization\SerializerInterface;
 use Symfony\Component\Messenger\Transport\TransportFactoryInterface;
 use Symfony\Component\Messenger\Transport\TransportInterface;
@@ -28,7 +28,7 @@ class AmqpTransportFactory implements TransportFactoryInterface
 
     public function __construct(SerializerInterface $serializer = null, bool $debug = false)
     {
-        $this->serializer = $serializer ?? Serializer::create();
+        $this->serializer = $serializer ?? new PhpSerializer();
         $this->debug = $debug;
     }
 
diff --git a/src/Symfony/Component/Messenger/Transport/Serialization/PhpSerializer.php b/src/Symfony/Component/Messenger/Transport/Serialization/PhpSerializer.php
new file mode 100644
index 0000000000000..ec6176c85ddca
--- /dev/null
+++ b/src/Symfony/Component/Messenger/Transport/Serialization/PhpSerializer.php
@@ -0,0 +1,45 @@
+<?php
+
+/*
+ * This file is part of the Symfony package.
+ *
+ * (c) Fabien Potencier <fabien@symfony.com>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace Symfony\Component\Messenger\Transport\Serialization;
+
+use Symfony\Component\Messenger\Envelope;
+use Symfony\Component\Messenger\Exception\InvalidArgumentException;
+
+/**
+ * @author Ryan Weaver<ryan@symfonycasts.com>
+ *
+ * @experimental in 4.2
+ */
+class PhpSerializer implements SerializerInterface
+{
+    /**
+     * {@inheritdoc}
+     */
+    public function decode(array $encodedEnvelope): Envelope
+    {
+        if (empty($encodedEnvelope['body'])) {
+            throw new InvalidArgumentException('Encoded envelope should have at least a "body".');
+        }
+
+        return unserialize($encodedEnvelope['body']);
+    }
+
+    /**
+     * {@inheritdoc}
+     */
+    public function encode(Envelope $envelope): array
+    {
+        return [
+            'body' => serialize($envelope),
+        ];
+    }
+}