diff --git a/rules-tests/TypeDeclaration/Rector/ClassMethod/AddParamTypeBasedOnPHPUnitDataProviderRector/Fixture/skip_yield_from_combined_with_yield.php.inc b/rules-tests/TypeDeclaration/Rector/ClassMethod/AddParamTypeBasedOnPHPUnitDataProviderRector/Fixture/skip_yield_from_combined_with_yield.php.inc
new file mode 100644
index 00000000000..4bd13a88e05
--- /dev/null
+++ b/rules-tests/TypeDeclaration/Rector/ClassMethod/AddParamTypeBasedOnPHPUnitDataProviderRector/Fixture/skip_yield_from_combined_with_yield.php.inc
@@ -0,0 +1,28 @@
+<?php
+
+namespace Rector\Tests\TypeDeclaration\Rector\ClassMethod\AddParamTypeBasedOnPHPUnitDataProviderRector\Fixture;
+
+use PHPUnit\Framework\TestCase;
+
+final class SkipYieldFromCombinedWithYield extends TestCase
+{
+    /**
+     * @dataProvider provideData
+     */
+    public function test($value): void
+    {
+    }
+
+    public static function provideData(): iterable
+    {
+        yield from self::provideMoreData();
+        yield ['name'];
+    }
+
+    public static function provideMoreData(): iterable
+    {
+        yield [100];
+    }
+}
+
+?>
diff --git a/rules-tests/TypeDeclaration/Rector/ClassMethod/AddParamTypeBasedOnPHPUnitDataProviderRector/Fixture/skip_yield_variable_multiple_types.php.inc b/rules-tests/TypeDeclaration/Rector/ClassMethod/AddParamTypeBasedOnPHPUnitDataProviderRector/Fixture/skip_yield_variable_multiple_types.php.inc
new file mode 100644
index 00000000000..0c81a3da095
--- /dev/null
+++ b/rules-tests/TypeDeclaration/Rector/ClassMethod/AddParamTypeBasedOnPHPUnitDataProviderRector/Fixture/skip_yield_variable_multiple_types.php.inc
@@ -0,0 +1,33 @@
+<?php
+
+namespace Rector\Tests\TypeDeclaration\Rector\ClassMethod\AddParamTypeBasedOnPHPUnitDataProviderRector\Fixture;
+
+use DateTimeImmutable;
+use PHPUnit\Framework\TestCase;
+
+final class SkipYieldVariableMultipleTypes extends TestCase
+{
+    /**
+     * @dataProvider provideData
+     */
+    public function test(bool $expected, $datumEzl): void
+    {
+    }
+
+    public static function provideData(): iterable
+    {
+        $erstZulassung = new DateTimeImmutable('-8 months');
+
+        $cases = [
+            [true, $erstZulassung],
+            [false, $erstZulassung],
+        ];
+
+        foreach ($cases as $case) {
+            yield $case;
+            yield [$case[0], $case[1]->format('Y-m-d')];
+        }
+    }
+}
+
+?>
diff --git a/rules-tests/TypeDeclaration/Rector/ClassMethod/AddParamTypeBasedOnPHPUnitDataProviderRector/FixtureUnion/yield_variable_multiple_types.php.inc b/rules-tests/TypeDeclaration/Rector/ClassMethod/AddParamTypeBasedOnPHPUnitDataProviderRector/FixtureUnion/yield_variable_multiple_types.php.inc
new file mode 100644
index 00000000000..3bb930b6852
--- /dev/null
+++ b/rules-tests/TypeDeclaration/Rector/ClassMethod/AddParamTypeBasedOnPHPUnitDataProviderRector/FixtureUnion/yield_variable_multiple_types.php.inc
@@ -0,0 +1,67 @@
+<?php
+
+namespace Rector\Tests\TypeDeclaration\Rector\ClassMethod\AddParamTypeBasedOnPHPUnitDataProviderRector\FixtureUnion;
+
+use DateTimeImmutable;
+use PHPUnit\Framework\TestCase;
+
+final class YieldVariableMultipleTypes extends TestCase
+{
+    /**
+     * @dataProvider provideData
+     */
+    public function test(bool $expected, $datumEzl): void
+    {
+    }
+
+    public static function provideData(): iterable
+    {
+        $erstZulassung = new DateTimeImmutable('-8 months');
+
+        $cases = [
+            [true, $erstZulassung],
+            [false, $erstZulassung],
+        ];
+
+        foreach ($cases as $case) {
+            yield $case;
+            yield [$case[0], $case[1]->format('Y-m-d')];
+        }
+    }
+}
+
+?>
+-----
+<?php
+
+namespace Rector\Tests\TypeDeclaration\Rector\ClassMethod\AddParamTypeBasedOnPHPUnitDataProviderRector\FixtureUnion;
+
+use DateTimeImmutable;
+use PHPUnit\Framework\TestCase;
+
+final class YieldVariableMultipleTypes extends TestCase
+{
+    /**
+     * @dataProvider provideData
+     */
+    public function test(bool $expected, \DateTimeImmutable|string $datumEzl): void
+    {
+    }
+
+    public static function provideData(): iterable
+    {
+        $erstZulassung = new DateTimeImmutable('-8 months');
+
+        $cases = [
+            [true, $erstZulassung],
+            [false, $erstZulassung],
+        ];
+
+        foreach ($cases as $case) {
+            yield $case;
+            yield [$case[0], $case[1]->format('Y-m-d')];
+        }
+    }
+}
+
+?>
diff --git a/rules-tests/TypeDeclaration/Rector/ClassMethod/AddParamTypeBasedOnPHPUnitDataProviderRector/UnionTest.php b/rules-tests/TypeDeclaration/Rector/ClassMethod/AddParamTypeBasedOnPHPUnitDataProviderRector/UnionTest.php
new file mode 100644
index 00000000000..4ef34239aaa
--- /dev/null
+++ b/rules-tests/TypeDeclaration/Rector/ClassMethod/AddParamTypeBasedOnPHPUnitDataProviderRector/UnionTest.php
@@ -0,0 +1,28 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Rector\Tests\TypeDeclaration\Rector\ClassMethod\AddParamTypeBasedOnPHPUnitDataProviderRector;
+
+use Iterator;
+use PHPUnit\Framework\Attributes\DataProvider;
+use Rector\Testing\PHPUnit\AbstractRectorTestCase;
+
+final class UnionTest extends AbstractRectorTestCase
+{
+    #[DataProvider('provideData')]
+    public function test(string $filePath): void
+    {
+        $this->doTestFile($filePath);
+    }
+
+    public static function provideData(): Iterator
+    {
+        return self::yieldFilesFromDirectory(__DIR__ . '/FixtureUnion');
+    }
+
+    public function provideConfigFilePath(): string
+    {
+        return __DIR__ . '/config/union_config.php';
+    }
+}
diff --git a/rules-tests/TypeDeclaration/Rector/ClassMethod/AddParamTypeBasedOnPHPUnitDataProviderRector/config/union_config.php b/rules-tests/TypeDeclaration/Rector/ClassMethod/AddParamTypeBasedOnPHPUnitDataProviderRector/config/union_config.php
new file mode 100644
index 00000000000..40a809d31f8
--- /dev/null
+++ b/rules-tests/TypeDeclaration/Rector/ClassMethod/AddParamTypeBasedOnPHPUnitDataProviderRector/config/union_config.php
@@ -0,0 +1,13 @@
+<?php
+
+declare(strict_types=1);
+
+use Rector\Config\RectorConfig;
+use Rector\TypeDeclaration\Rector\ClassMethod\AddParamTypeBasedOnPHPUnitDataProviderRector;
+use Rector\ValueObject\PhpVersionFeature;
+
+return static function (RectorConfig $rectorConfig): void {
+    $rectorConfig->rule(AddParamTypeBasedOnPHPUnitDataProviderRector::class);
+
+    $rectorConfig->phpVersion(PhpVersionFeature::UNION_TYPES);
+};
diff --git a/rules/TypeDeclaration/TypeAnalyzer/ParameterTypeFromDataProviderResolver.php b/rules/TypeDeclaration/TypeAnalyzer/ParameterTypeFromDataProviderResolver.php
index 9d008d69a37..cf8cf419866 100644
--- a/rules/TypeDeclaration/TypeAnalyzer/ParameterTypeFromDataProviderResolver.php
+++ b/rules/TypeDeclaration/TypeAnalyzer/ParameterTypeFromDataProviderResolver.php
@@ -5,14 +5,17 @@
 namespace Rector\TypeDeclaration\TypeAnalyzer;
 
 use PhpParser\Node\ArrayItem;
+use PhpParser\Node\Expr;
 use PhpParser\Node\Expr\Array_;
 use PhpParser\Node\Expr\Yield_;
+use PhpParser\Node\Expr\YieldFrom;
 use PhpParser\Node\Stmt\ClassMethod;
 use PhpParser\Node\Stmt\Return_;
 use PHPStan\Type\Constant\ConstantArrayType;
 use PHPStan\Type\MixedType;
 use PHPStan\Type\Type;
 use PHPStan\Type\TypeCombinator;
+use PHPStan\Type\UnionType;
 use Rector\NodeTypeResolver\NodeTypeResolver;
 use Rector\NodeTypeResolver\PHPStan\Type\TypeFactory;
 use Rector\PhpParser\Node\BetterNodeFinder;
@@ -51,6 +54,16 @@ private function resolveParameterTypeFromDataProvider(
             return $this->resolveReturnStaticArrayTypeByParameterPosition($returns, $parameterPosition);
         }
 
+        $yieldFromNodes = $this->betterNodeFinder->findInstancesOfInFunctionLikeScoped(
+            $dataProviderClassMethod,
+            YieldFrom::class
+        );
+
+        // "yield from" data sets are not resolved here → the resolved type would be incomplete
+        if ($yieldFromNodes !== []) {
+            return new MixedType();
+        }
+
         /** @var Yield_[] $yields */
         $yields = $this->betterNodeFinder->findInstancesOfInFunctionLikeScoped($dataProviderClassMethod, Yield_::class);
         return $this->resolveYieldStaticArrayTypeByParameterPosition($yields, $parameterPosition);
@@ -83,22 +96,25 @@ private function resolveYieldStaticArrayTypeByParameterPosition(array $yields, i
         $paramOnPositionTypes = [];
 
         foreach ($yields as $yield) {
-            if (! $yield->value instanceof Array_) {
-                continue;
+            if (! $yield->value instanceof Expr) {
+                return new MixedType();
             }
 
-            $type = $this->getTypeFromClassMethodYield($yield->value);
+            $constantArrayTypes = $this->resolveYieldedConstantArrayTypes($yield->value);
 
-            if (! $type instanceof ConstantArrayType) {
-                return $type;
+            // one of the yielded data sets cannot be resolved → the resolved type would be incomplete
+            if ($constantArrayTypes === []) {
+                return new MixedType();
             }
 
-            foreach ($type->getValueTypes() as $position => $valueType) {
-                if ($position !== $parameterPosition) {
-                    continue;
-                }
+            foreach ($constantArrayTypes as $constantArrayType) {
+                foreach ($constantArrayType->getValueTypes() as $position => $valueType) {
+                    if ($position !== $parameterPosition) {
+                        continue;
+                    }
 
-                $paramOnPositionTypes[] = $valueType;
+                    $paramOnPositionTypes[] = $valueType;
+                }
             }
         }
 
@@ -109,16 +125,32 @@ private function resolveYieldStaticArrayTypeByParameterPosition(array $yields, i
         return $this->typeFactory->createMixedPassedOrUnionType($paramOnPositionTypes);
     }
 
-    private function getTypeFromClassMethodYield(Array_ $classMethodYieldArray): MixedType|ConstantArrayType
+    /**
+     * @return ConstantArrayType[]
+     */
+    private function resolveYieldedConstantArrayTypes(Expr $expr): array
     {
-        $arrayType = $this->nodeTypeResolver->getType($classMethodYieldArray);
+        $yieldedType = $this->nodeTypeResolver->getType($expr);
 
-        // impossible to resolve
-        if (! $arrayType instanceof ConstantArrayType) {
-            return new MixedType();
+        if ($yieldedType instanceof ConstantArrayType) {
+            return [$yieldedType];
+        }
+
+        if (! $yieldedType instanceof UnionType) {
+            return [];
+        }
+
+        $constantArrayTypes = [];
+        foreach ($yieldedType->getTypes() as $unionedType) {
+            // impossible to resolve
+            if (! $unionedType instanceof ConstantArrayType) {
+                return [];
+            }
+
+            $constantArrayTypes[] = $unionedType;
         }
 
-        return $arrayType;
+        return $constantArrayTypes;
     }
 
     /**