diff --git a/src/Symfony/Component/Serializer/Normalizer/AbstractNormalizer.php b/src/Symfony/Component/Serializer/Normalizer/AbstractNormalizer.php
index f07be74c2e8ab..b46ea1a2676a5 100644
--- a/src/Symfony/Component/Serializer/Normalizer/AbstractNormalizer.php
+++ b/src/Symfony/Component/Serializer/Normalizer/AbstractNormalizer.php
@@ -408,16 +408,22 @@ protected function instantiateObject(array &$data, string $class, array &$contex
                         continue;
                     }
 
-                    $constructorParameterType = 'unknown';
+                    $constructorParameterTypes = [];
                     $reflectionType = $constructorParameter->getType();
-                    if ($reflectionType instanceof \ReflectionNamedType) {
-                        $constructorParameterType = $reflectionType->getName();
+                    if ($reflectionType instanceof \ReflectionUnionType) {
+                        foreach ($reflectionType->getTypes() as $reflectionType) {
+                            $constructorParameterTypes[] = (string) $reflectionType;
+                        }
+                    } elseif ($reflectionType instanceof \ReflectionType) {
+                        $constructorParameterTypes[] = (string) $reflectionType;
+                    } else {
+                        $constructorParameterTypes[] = 'unknown';
                     }
 
                     $exception = NotNormalizableValueException::createForUnexpectedDataType(
                         \sprintf('Failed to create object because the class misses the "%s" property.', $constructorParameter->name),
                         null,
-                        [$constructorParameterType],
+                        $constructorParameterTypes,
                         $attributeContext['deserialization_path'] ?? null,
                         true
                     );
diff --git a/src/Symfony/Component/Serializer/Tests/Fixtures/DummyWithUnion.php b/src/Symfony/Component/Serializer/Tests/Fixtures/DummyWithUnion.php
new file mode 100644
index 0000000000000..c40bc1867248b
--- /dev/null
+++ b/src/Symfony/Component/Serializer/Tests/Fixtures/DummyWithUnion.php
@@ -0,0 +1,24 @@
+<?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\Serializer\Tests\Fixtures;
+
+/**
+ * @author Dmitrii <github.com/d-mitrofanov-v>
+ */
+class DummyWithUnion
+{
+    public function __construct(
+        public int|float $value,
+        public string|int $value2,
+    ) {
+    }
+}
diff --git a/src/Symfony/Component/Serializer/Tests/SerializerTest.php b/src/Symfony/Component/Serializer/Tests/SerializerTest.php
index db16e81db0faa..b1b56e5c07aff 100644
--- a/src/Symfony/Component/Serializer/Tests/SerializerTest.php
+++ b/src/Symfony/Component/Serializer/Tests/SerializerTest.php
@@ -62,6 +62,7 @@
 use Symfony\Component\Serializer\Tests\Fixtures\DummyObjectWithEnumConstructor;
 use Symfony\Component\Serializer\Tests\Fixtures\DummyObjectWithEnumProperty;
 use Symfony\Component\Serializer\Tests\Fixtures\DummyWithObjectOrNull;
+use Symfony\Component\Serializer\Tests\Fixtures\DummyWithUnion;
 use Symfony\Component\Serializer\Tests\Fixtures\DummyWithVariadicParameter;
 use Symfony\Component\Serializer\Tests\Fixtures\FalseBuiltInDummy;
 use Symfony\Component\Serializer\Tests\Fixtures\FooImplementationDummy;
@@ -1392,6 +1393,60 @@ public function testCollectDenormalizationErrorsWithInvalidConstructorTypes()
         $this->assertSame($expected, $exceptionsAsArray);
     }
 
+    public function testCollectDenormalizationErrorsWithUnionConstructorTypes()
+    {
+        $json = '{}';
+
+        $serializer = new Serializer(
+            [new ObjectNormalizer()],
+            ['json' => new JsonEncoder()]
+        );
+
+        try {
+            $serializer->deserialize(
+                $json,
+                DummyWithUnion::class,
+                'json',
+                [DenormalizerInterface::COLLECT_DENORMALIZATION_ERRORS => true]
+            );
+
+            $this->fail();
+        } catch (\Throwable $th) {
+            $this->assertInstanceOf(PartialDenormalizationException::class, $th);
+        }
+
+        $exceptionsAsArray = array_map(fn (NotNormalizableValueException $e): array => [
+            'currentType' => $e->getCurrentType(),
+            'expectedTypes' => $e->getExpectedTypes(),
+            'path' => $e->getPath(),
+            'useMessageForUser' => $e->canUseMessageForUser(),
+            'message' => $e->getMessage(),
+        ], $th->getErrors());
+
+        $expected = [
+            [
+                'currentType' => 'null',
+                'expectedTypes' => [
+                    'int', 'float',
+                ],
+                'path' => 'value',
+                'useMessageForUser' => true,
+                'message' => 'Failed to create object because the class misses the "value" property.',
+            ],
+            [
+                'currentType' => 'null',
+                'expectedTypes' => [
+                    'string', 'int',
+                ],
+                'path' => 'value2',
+                'useMessageForUser' => true,
+                'message' => 'Failed to create object because the class misses the "value2" property.',
+            ],
+        ];
+
+        $this->assertSame($expected, $exceptionsAsArray);
+    }
+
     public function testCollectDenormalizationErrorsWithEnumConstructor()
     {
         $serializer = new Serializer(