diff --git a/rules-tests/TypeDeclarationDocblocks/Rector/ClassMethod/DocblockReturnArrayFromDirectArrayInstanceRector/Fixture/with_duplicated_nested_array.php.inc b/rules-tests/TypeDeclarationDocblocks/Rector/ClassMethod/DocblockReturnArrayFromDirectArrayInstanceRector/Fixture/with_duplicated_nested_array.php.inc
new file mode 100644
index 00000000000..63242d692e1
--- /dev/null
+++ b/rules-tests/TypeDeclarationDocblocks/Rector/ClassMethod/DocblockReturnArrayFromDirectArrayInstanceRector/Fixture/with_duplicated_nested_array.php.inc
@@ -0,0 +1,54 @@
+<?php
+
+namespace Rector\Tests\TypeDeclarationDocblocks\Rector\ClassMethod\DocblockReturnArrayFromDirectArrayInstanceRector\Fixture;
+
+/**
+ * @see https://github.com/codeigniter4/CodeIgniter4/blob/89fee62b666c07550197203a94fb7dd94303d7ca/tests/system/CodeIgniterTest.php#L893
+ */
+final class WithDuplicatedNestedArray
+{
+    public static function run(): iterable
+    {
+        $testingUrls = [
+            'test',
+            'test?important_parameter=1',
+        ];
+
+        return [
+            '$cacheQueryString=false' => [false, 1, $testingUrls],
+            '$cacheQueryString=true' => [true, 5, $testingUrls],
+            '$cacheQueryString=array' => [['important_parameter'], 3, $testingUrls],
+        ];
+    }
+}
+
+?>
+-----
+<?php
+
+namespace Rector\Tests\TypeDeclarationDocblocks\Rector\ClassMethod\DocblockReturnArrayFromDirectArrayInstanceRector\Fixture;
+
+/**
+ * @see https://github.com/codeigniter4/CodeIgniter4/blob/89fee62b666c07550197203a94fb7dd94303d7ca/tests/system/CodeIgniterTest.php#L893
+ */
+final class WithDuplicatedNestedArray
+{
+    /**
+     * @return array<string, string[][]|bool[]|int[]>
+     */
+    public static function run(): iterable
+    {
+        $testingUrls = [
+            'test',
+            'test?important_parameter=1',
+        ];
+
+        return [
+            '$cacheQueryString=false' => [false, 1, $testingUrls],
+            '$cacheQueryString=true' => [true, 5, $testingUrls],
+            '$cacheQueryString=array' => [['important_parameter'], 3, $testingUrls],
+        ];
+    }
+}
+
+?>
diff --git a/src/PHPStanStaticTypeMapper/TypeMapper/UnionTypeMapper.php b/src/PHPStanStaticTypeMapper/TypeMapper/UnionTypeMapper.php
index e900d9e01eb..fd162b7cfc0 100644
--- a/src/PHPStanStaticTypeMapper/TypeMapper/UnionTypeMapper.php
+++ b/src/PHPStanStaticTypeMapper/TypeMapper/UnionTypeMapper.php
@@ -19,6 +19,7 @@
 use PHPStan\Type\Type;
 use PHPStan\Type\UnionType;
 use Rector\BetterPhpDocParser\ValueObject\Type\BracketsAwareUnionTypeNode;
+use Rector\BetterPhpDocParser\ValueObject\Type\SpacingAwareArrayTypeNode;
 use Rector\NodeAnalyzer\PropertyAnalyzer;
 use Rector\Php\PhpVersionProvider;
 use Rector\PHPStanStaticTypeMapper\Contract\TypeMapperInterface;
@@ -57,12 +58,32 @@ public function getNodeClass(): string
     public function mapToPHPStanPhpDocTypeNode(Type $type): TypeNode
     {
         $unionTypesNodes = [];
+        $existingTypes = [];
+
         foreach ($type->getTypes() as $unionedType) {
             if ($unionedType instanceof ArrayType && $unionedType->getItemType() instanceof NeverType) {
                 $unionedType = new ArrayType($unionedType->getKeyType(), new MixedType());
             }
 
-            $unionTypesNodes[] = $this->phpStanStaticTypeMapper->mapToPHPStanPhpDocTypeNode($unionedType);
+            $unionedType = $this->phpStanStaticTypeMapper->mapToPHPStanPhpDocTypeNode($unionedType);
+
+            if ($unionedType instanceof SpacingAwareArrayTypeNode && $unionedType->type instanceof BracketsAwareUnionTypeNode) {
+                foreach ($unionedType->type->types as $key => $innerTypeNode) {
+                    $printedInnerType = (string) $innerTypeNode;
+                    if (in_array($printedInnerType, $existingTypes, true)) {
+                        unset($unionedType->type->types[$key]);
+                        continue;
+                    }
+
+                    $existingTypes[] = $printedInnerType;
+                }
+
+                if ($unionedType->type->types === []) {
+                    continue;
+                }
+            }
+
+            $unionTypesNodes[] = $unionedType;
         }
 
         return new BracketsAwareUnionTypeNode($unionTypesNodes);