diff --git a/Neos.Flow/Tests/Functional/Reflection/Fixtures/DummyClassWithUnionTypeAnnotations.php b/Neos.Flow/Tests/Functional/Reflection/Fixtures/DummyClassWithUnionTypeAnnotations.php
new file mode 100644
index 0000000000..6fbfb9256b
--- /dev/null
+++ b/Neos.Flow/Tests/Functional/Reflection/Fixtures/DummyClassWithUnionTypeAnnotations.php
@@ -0,0 +1,51 @@
+<?php
+namespace Neos\Flow\Tests\Functional\Reflection\Fixtures;
+
+/*
+ * This file is part of the Neos.Flow package.
+ *
+ * (c) Contributors of the Neos Project - www.neos.io
+ *
+ * This package is Open Source Software. For the full copyright and license
+ * information, please view the LICENSE file which was distributed with this
+ * source code.
+ */
+
+/**
+ * Dummy class for the Reflection tests
+ *
+ */
+class DummyClassWithUnionTypeAnnotations
+{
+    /**
+     * @param string|false $parameterA
+     * @param false|DummyClassWithUnionTypeAnnotations $parameterB
+     * @param false | DummyClassWithUnionTypeAnnotations $parameterB1 Same as B but with spaces in between
+     * @param DummyClassWithUnionTypeAnnotations|null $parameterC
+     * @return void
+     */
+    public function methodWithUnionParameters($parameterA, $parameterB, $parameterB1, $parameterC)
+    {
+    }
+
+    /**
+     * @return string|false
+     */
+    public function methodWithUnionReturnTypeA()
+    {
+    }
+
+    /**
+     * @return false|DummyClassWithUnionTypeAnnotations
+     */
+    public function methodWithUnionReturnTypesB()
+    {
+    }
+
+    /**
+     * @return DummyClassWithUnionTypeAnnotations|null
+     */
+    public function methodWithUnionReturnTypesC()
+    {
+    }
+}
diff --git a/Neos.Flow/Tests/Functional/Reflection/Fixtures/PHP8/DummyClassWithUnionTypeHints.php b/Neos.Flow/Tests/Functional/Reflection/Fixtures/DummyClassWithUnionTypeHints.php
similarity index 70%
rename from Neos.Flow/Tests/Functional/Reflection/Fixtures/PHP8/DummyClassWithUnionTypeHints.php
rename to Neos.Flow/Tests/Functional/Reflection/Fixtures/DummyClassWithUnionTypeHints.php
index 25e2347473..7a47bb255f 100644
--- a/Neos.Flow/Tests/Functional/Reflection/Fixtures/PHP8/DummyClassWithUnionTypeHints.php
+++ b/Neos.Flow/Tests/Functional/Reflection/Fixtures/DummyClassWithUnionTypeHints.php
@@ -1,5 +1,5 @@
 <?php
-namespace Neos\Flow\Tests\Functional\Reflection\Fixtures\PHP8;
+namespace Neos\Flow\Tests\Functional\Reflection\Fixtures;
 
 /*
  * This file is part of the Neos.Flow package.
@@ -17,6 +17,13 @@
  */
 class DummyClassWithUnionTypeHints
 {
+    public function methodWithUnionParameters(
+        string|false $parameterA,
+        false|DummyClassWithUnionTypeHints $parameterB,
+        null|DummyClassWithUnionTypeHints $parameterC
+    ): void {
+    }
+
     public function methodWithUnionReturnTypeA(): string|false
     {
     }
diff --git a/Neos.Flow/Tests/Functional/Reflection/ReflectionServiceTest.php b/Neos.Flow/Tests/Functional/Reflection/ReflectionServiceTest.php
index c2cb5ecf95..fc95a126e6 100644
--- a/Neos.Flow/Tests/Functional/Reflection/ReflectionServiceTest.php
+++ b/Neos.Flow/Tests/Functional/Reflection/ReflectionServiceTest.php
@@ -12,12 +12,12 @@
  */
 
 use Neos\Flow\Reflection\ReflectionService;
+use Neos\Flow\Tests\Functional\Persistence;
+use Neos\Flow\Tests\Functional\Reflection;
 use Neos\Flow\Tests\Functional\Reflection\Fixtures\Model\SubEntity;
 use Neos\Flow\Tests\Functional\Reflection\Fixtures\Model\SubSubEntity;
 use Neos\Flow\Tests\Functional\Reflection\Fixtures\Model\SubSubSubEntity;
 use Neos\Flow\Tests\FunctionalTestCase;
-use Neos\Flow\Tests\Functional\Reflection;
-use Neos\Flow\Tests\Functional\Persistence;
 
 /**
  * Functional tests for the Reflection Service features
@@ -356,15 +356,121 @@ public function annotatedArrayTypeHintsWorkCorrectly()
      */
     public function unionReturnTypesWorkCorrectly()
     {
-        if (PHP_MAJOR_VERSION < 8) {
-            $this->markTestSkipped('Only for PHP 8 with UnionTypes');
-        }
-        $returnTypeA = $this->reflectionService->getMethodDeclaredReturnType(Reflection\Fixtures\PHP8\DummyClassWithUnionTypeHints::class, 'methodWithUnionReturnTypeA');
-        $returnTypeB = $this->reflectionService->getMethodDeclaredReturnType(Reflection\Fixtures\PHP8\DummyClassWithUnionTypeHints::class, 'methodWithUnionReturnTypesB');
-        $returnTypeC = $this->reflectionService->getMethodDeclaredReturnType(Reflection\Fixtures\PHP8\DummyClassWithUnionTypeHints::class, 'methodWithUnionReturnTypesC');
+        $returnTypes = [
+            'returnTypeA' => $this->reflectionService->getMethodDeclaredReturnType(Fixtures\DummyClassWithUnionTypeHints::class, 'methodWithUnionReturnTypeA'),
+            'returnTypeB' => $this->reflectionService->getMethodDeclaredReturnType(Fixtures\DummyClassWithUnionTypeHints::class, 'methodWithUnionReturnTypesB'),
+            'returnTypeC' => $this->reflectionService->getMethodDeclaredReturnType(Fixtures\DummyClassWithUnionTypeHints::class, 'methodWithUnionReturnTypesC'),
+        ];
+
+        self::assertEquals(
+            [
+                'returnTypeA' => 'string|false',
+                'returnTypeB' => '\Neos\Flow\Tests\Functional\Reflection\Fixtures\DummyClassWithUnionTypeHints|false',
+                'returnTypeC' => '?\Neos\Flow\Tests\Functional\Reflection\Fixtures\DummyClassWithUnionTypeHints',
+            ],
+            $returnTypes
+        );
+    }
+
+    /**
+     * @test
+     */
+    public function unionParameterTypesWorkCorrectly()
+    {
+        $methodWithUnionParameters = $this->reflectionService->getMethodParameters(Fixtures\DummyClassWithUnionTypeHints::class, 'methodWithUnionParameters');
+
+        $methodWithUnionParametersReduced = array_map(
+            fn (array $item) => [
+                'type' => $item['type'],
+                'class' => $item['class'],
+                'allowsNull' => $item['allowsNull'],
+            ],
+            $methodWithUnionParameters
+        );
+
+        self::assertEquals(
+            [
+                'parameterA' => [
+                    'type' => 'string|false',
+                    'class' => 'string|false',
+                    'allowsNull' => false,
+                ],
+                'parameterB' => [
+                    'type' => 'Neos\Flow\Tests\Functional\Reflection\Fixtures\DummyClassWithUnionTypeHints|false',
+                    'class' => 'Neos\Flow\Tests\Functional\Reflection\Fixtures\DummyClassWithUnionTypeHints|false',
+                    'allowsNull' => false,
+                ],
+                'parameterC' => [
+                    'type' => 'Neos\Flow\Tests\Functional\Reflection\Fixtures\DummyClassWithUnionTypeHints',
+                    'class' => 'Neos\Flow\Tests\Functional\Reflection\Fixtures\DummyClassWithUnionTypeHints',
+                    'allowsNull' => true,
+                ],
+            ],
+            $methodWithUnionParametersReduced
+        );
+    }
 
-        self::assertEquals('string|false', $returnTypeA);
-        self::assertEquals('\Neos\Flow\Tests\Functional\Reflection\Fixtures\PHP8\DummyClassWithUnionTypeHints|false', $returnTypeB);
-        self::assertEquals('?\Neos\Flow\Tests\Functional\Reflection\Fixtures\PHP8\DummyClassWithUnionTypeHints', $returnTypeC);
+    /**
+     * @test
+     */
+    public function unionReturnTypeAnnotationsWorkCorrectly()
+    {
+        $returnTypes = [
+            'returnTypeA' => $this->reflectionService->getMethodDeclaredReturnType(Fixtures\DummyClassWithUnionTypeAnnotations::class, 'methodWithUnionReturnTypeA'),
+            'returnTypeB' => $this->reflectionService->getMethodDeclaredReturnType(Fixtures\DummyClassWithUnionTypeAnnotations::class, 'methodWithUnionReturnTypesB'),
+            'returnTypeC' => $this->reflectionService->getMethodDeclaredReturnType(Fixtures\DummyClassWithUnionTypeAnnotations::class, 'methodWithUnionReturnTypesC'),
+        ];
+
+        self::assertEquals(
+            [
+                'returnTypeA' => 'string|false',
+                'returnTypeB' => '\Neos\Flow\Tests\Functional\Reflection\Fixtures\DummyClassWithUnionTypeAnnotations|false',
+                'returnTypeC' => '?\Neos\Flow\Tests\Functional\Reflection\Fixtures\DummyClassWithUnionTypeAnnotations',
+            ],
+            $returnTypes
+        );
+    }
+
+    /**
+     * @test
+     */
+    public function unionParameterTypeAnnotationsWorkCorrectly()
+    {
+        $methodWithUnionParameters = $this->reflectionService->getMethodParameters(Fixtures\DummyClassWithUnionTypeAnnotations::class, 'methodWithUnionParameters');
+
+        $methodWithUnionParametersReduced = array_map(
+            fn (array $item) => [
+                'type' => $item['type'],
+                'class' => $item['class'],
+                'allowsNull' => $item['allowsNull'],
+            ],
+            $methodWithUnionParameters
+        );
+
+        self::assertEquals(
+            [
+                'parameterA' => [
+                    'type' => 'string|false',
+                    'class' => 'string|false',
+                    'allowsNull' => false,
+                ],
+                'parameterB' => [
+                    'type' => 'Neos\Flow\Tests\Functional\Reflection\Fixtures\DummyClassWithUnionTypeAnnotations|false',
+                    'class' => 'Neos\Flow\Tests\Functional\Reflection\Fixtures\DummyClassWithUnionTypeAnnotations|false',
+                    'allowsNull' => false,
+                ],
+                'parameterB1' => [
+                    'type' => 'Neos\Flow\Tests\Functional\Reflection\Fixtures\DummyClassWithUnionTypeAnnotations|false',
+                    'class' => 'Neos\Flow\Tests\Functional\Reflection\Fixtures\DummyClassWithUnionTypeAnnotations|false',
+                    'allowsNull' => false,
+                ],
+                'parameterC' => [
+                    'type' => 'Neos\Flow\Tests\Functional\Reflection\Fixtures\DummyClassWithUnionTypeAnnotations',
+                    'class' => 'Neos\Flow\Tests\Functional\Reflection\Fixtures\DummyClassWithUnionTypeAnnotations',
+                    'allowsNull' => true,
+                ],
+            ],
+            $methodWithUnionParametersReduced
+        );
     }
 }