diff --git a/src/Drupal/DrupalServiceDefinition.php b/src/Drupal/DrupalServiceDefinition.php
index 7dce38d2..c0d0046b 100644
--- a/src/Drupal/DrupalServiceDefinition.php
+++ b/src/Drupal/DrupalServiceDefinition.php
@@ -5,6 +5,7 @@
 use PHPStan\Type\ObjectType;
 use PHPStan\Type\StringType;
 use PHPStan\Type\Type;
+use PHPStan\Type\UnionType;
 
 class DrupalServiceDefinition
 {
@@ -44,6 +45,11 @@ class DrupalServiceDefinition
      */
     private $alias;
 
+    /**
+     * @var array<string, \mglaman\PHPStanDrupal\Drupal\DrupalServiceDefinition>
+     */
+    private $decorators = [];
+
     public function __construct(string $id, ?string $class, bool $public = true, ?string $alias = null)
     {
         $this->id = $id;
@@ -109,6 +115,28 @@ public function getType(): Type
             return new StringType();
         }
 
+        $decorating_services = $this->getDecorators();
+        if (count($decorating_services) !== 0) {
+            $combined_services = [];
+            $combined_services[] = new ObjectType($this->getClass() ?? $this->id);
+            foreach ($decorating_services as $service_id => $service_definition) {
+                $combined_services[] = $service_definition->getType();
+            }
+            return new UnionType($combined_services);
+        }
         return new ObjectType($this->getClass() ?? $this->id);
     }
+
+    public function addDecorator(DrupalServiceDefinition $definition): void
+    {
+        $this->decorators[$definition->getId()] = $definition;
+    }
+
+    /**
+     * @return array<string, \mglaman\PHPStanDrupal\Drupal\DrupalServiceDefinition>
+     */
+    public function getDecorators(): array
+    {
+        return $this->decorators;
+    }
 }
diff --git a/src/Drupal/ServiceMap.php b/src/Drupal/ServiceMap.php
index 8c2c4433..6809e424 100644
--- a/src/Drupal/ServiceMap.php
+++ b/src/Drupal/ServiceMap.php
@@ -23,6 +23,7 @@ public function getServices(): array
     public function setDrupalServices(array $drupalServices): void
     {
         self::$services = [];
+        $decorators = [];
 
         foreach ($drupalServices as $serviceId => $serviceDefinition) {
             if (isset($serviceDefinition['alias'], $drupalServices[$serviceDefinition['alias']])) {
@@ -32,6 +33,10 @@ public function setDrupalServices(array $drupalServices): void
                 $serviceDefinition = $this->resolveParentDefinition($serviceDefinition['parent'], $serviceDefinition, $drupalServices);
             }
 
+            if (isset($serviceDefinition['decorates'])) {
+                $decorators[$serviceDefinition['decorates']][] = $serviceId;
+            }
+
             // @todo support factories
             if (!isset($serviceDefinition['class'])) {
                 if (class_exists($serviceId)) {
@@ -51,6 +56,12 @@ public function setDrupalServices(array $drupalServices): void
                 self::$services[$serviceId]->setDeprecated(true, $deprecated);
             }
         }
+
+        foreach ($decorators as $decorated_service_id => $services) {
+            foreach ($services as $dcorating_service_id) {
+                self::$services[$decorated_service_id]->addDecorator(self::$services[$dcorating_service_id]);
+            }
+        }
     }
 
     private function resolveParentDefinition(string $parentId, array $serviceDefinition, array $drupalServices): array
diff --git a/tests/src/ServiceMapFactoryTest.php b/tests/src/ServiceMapFactoryTest.php
index 5a6fa640..835a1163 100644
--- a/tests/src/ServiceMapFactoryTest.php
+++ b/tests/src/ServiceMapFactoryTest.php
@@ -5,6 +5,8 @@
 use Drupal\Core\Logger\LoggerChannel;
 use mglaman\PHPStanDrupal\Drupal\DrupalServiceDefinition;
 use mglaman\PHPStanDrupal\Drupal\ServiceMap;
+use PHPStan\Type\ObjectType;
+use PHPStan\Type\UnionType;
 use PHPUnit\Framework\TestCase;
 
 final class ServiceMapFactoryTest extends TestCase
@@ -93,6 +95,14 @@ public function testFactory(string $id, callable $validator): void
             ],
             'Psr\Log\LoggerInterface $loggerWorkspaces' => [
                 'alias' => 'logger.channel.workspaces'
+            ],
+            'service_map.base_to_be_decorated' => [
+                'class' => 'Drupal\service_map\Base',
+                'abstract' => true,
+            ],
+            'service_map.deocrating_base' => [
+                'decorates' => 'service_map.base_to_be_decorated',
+                'class' => 'Drupal\service_map\SecondBase',
             ]
         ]);
         $validator($service->getService($id));
@@ -212,6 +222,17 @@ function (DrupalServiceDefinition $service): void {
                 self::assertEquals(LoggerChannel::class, $service->getClass());
             }
         ];
+        yield [
+            'service_map.base_to_be_decorated',
+            function (DrupalServiceDefinition $service): void {
+              $combined_class = [
+                new ObjectType('Drupal\service_map\Base'),
+                new ObjectType('Drupal\service_map\SecondBase')
+              ];
+              $expected_class = new UnionType($combined_class);
+              self::assertEquals($expected_class, $service->getType());
+            }
+        ];
     }
 
 }