diff --git a/src/SimpleDTO.php b/src/SimpleDTO.php
index 0499461..6c60a61 100644
--- a/src/SimpleDTO.php
+++ b/src/SimpleDTO.php
@@ -400,14 +400,35 @@ private function formatArrayableValue(mixed $value): array
     {
         return match (true) {
             is_array($value) => $value,
-            $value instanceof Collection => $value->toArray(),
-            $value instanceof Model => $value->toArray(),
+            $value instanceof Collection => $this->transformCollectionToArray($value),
+            $value instanceof Model => $this->transformModelToArray($value),
             $value instanceof SimpleDTO => $this->transformDTOToArray($value),
             is_object($value) => (array) $value,
             default => [],
         };
     }
 
+    private function transformCollectionToArray(Collection $collection): array
+    {
+        return $collection->map(function ($item) {
+            return $this->isArrayable($item)
+                ? $this->formatArrayableValue($item)
+                : $item;
+        })->toArray();
+    }
+
+    private function transformModelToArray(Model $model): array
+    {
+        $result = [];
+        foreach ($model->getAttributes() as $key => $value) {
+            $result[$key] = $this->isArrayable($value)
+                ? $this->formatArrayableValue($value)
+                : $value;
+        }
+
+        return $result;
+    }
+
     private function transformDTOToArray(SimpleDTO $dto): array
     {
         $result = [];
diff --git a/tests/Datasets/UserNestedCollectionDTO.php b/tests/Datasets/UserNestedCollectionDTO.php
new file mode 100644
index 0000000..3288aad
--- /dev/null
+++ b/tests/Datasets/UserNestedCollectionDTO.php
@@ -0,0 +1,37 @@
+<?php
+
+declare(strict_types=1);
+
+namespace WendellAdriel\ValidatedDTO\Tests\Datasets;
+
+use Illuminate\Support\Collection;
+use WendellAdriel\ValidatedDTO\Casting\CollectionCast;
+use WendellAdriel\ValidatedDTO\Casting\DTOCast;
+use WendellAdriel\ValidatedDTO\ValidatedDTO;
+
+class UserNestedCollectionDTO extends ValidatedDTO
+{
+    public Collection $names;
+
+    public string $email;
+
+    protected function rules(): array
+    {
+        return [
+            'names' => ['required', 'array'],
+            'email' => ['required', 'email'],
+        ];
+    }
+
+    protected function defaults(): array
+    {
+        return [];
+    }
+
+    protected function casts(): array
+    {
+        return [
+            'names' => new CollectionCast(new DTOCast(NameDTO::class)),
+        ];
+    }
+}
diff --git a/tests/Unit/ValidatedDTOTest.php b/tests/Unit/ValidatedDTOTest.php
index 99c2c64..b62e1f3 100644
--- a/tests/Unit/ValidatedDTOTest.php
+++ b/tests/Unit/ValidatedDTOTest.php
@@ -16,6 +16,7 @@
 use WendellAdriel\ValidatedDTO\Tests\Datasets\NullableDTO;
 use WendellAdriel\ValidatedDTO\Tests\Datasets\User;
 use WendellAdriel\ValidatedDTO\Tests\Datasets\UserDTO;
+use WendellAdriel\ValidatedDTO\Tests\Datasets\UserNestedCollectionDTO;
 use WendellAdriel\ValidatedDTO\Tests\Datasets\UserNestedDTO;
 use WendellAdriel\ValidatedDTO\Tests\Datasets\ValidatedDTOInstance;
 use WendellAdriel\ValidatedDTO\ValidatedDTO;
@@ -200,78 +201,129 @@ public function __invoke()
 });
 
 it('validates that the ValidatedDTO can be converted into an array', function () {
-    $validatedDTO = new ValidatedDTOInstance(['name' => $this->subject_name]);
+    $dataStructure = ['name' => $this->subject_name];
+    $validatedDTO = new ValidatedDTOInstance($dataStructure);
 
     expect($validatedDTO)->toArray()
-        ->toBe(['name' => $this->subject_name]);
+        ->toBe($dataStructure);
 });
 
 it('validates that the ValidatedDTO can be converted into a JSON string', function () {
-    $validatedDTO = new ValidatedDTOInstance(['name' => $this->subject_name]);
+    $dataStructure = ['name' => $this->subject_name];
+    $validatedDTO = new ValidatedDTOInstance($dataStructure);
 
     expect($validatedDTO)->toJson()
-        ->toBe('{"name":"' . $this->subject_name . '"}');
+        ->toBe(json_encode($dataStructure));
 });
 
 it('validates that the ValidatedDTO can be converted into a pretty JSON string', function () {
-    $validatedDTO = new ValidatedDTOInstance(['name' => $this->subject_name]);
+    $dataStructure = ['name' => $this->subject_name];
+    $validatedDTO = new ValidatedDTOInstance($dataStructure);
 
     expect($validatedDTO)->toPrettyJson()
-        ->toBe(json_encode(['name' => $this->subject_name], JSON_PRETTY_PRINT));
+        ->toBe(json_encode($dataStructure, JSON_PRETTY_PRINT));
 });
 
 it('validates that the ValidatedDTO with nested data can be converted into an array', function () {
-    $validatedDTO = new UserNestedDTO([
+    $dataStructure = [
         'name' => [
             'first_name' => $this->subject_name,
             'last_name' => 'Doe',
         ],
         'email' => $this->subject_email,
-    ]);
+    ];
+    $validatedDTO = new UserNestedDTO($dataStructure);
 
     expect($validatedDTO)->toArray()
-        ->toBe([
-            'name' => [
-                'first_name' => $this->subject_name,
-                'last_name' => 'Doe',
-            ],
-            'email' => $this->subject_email,
-        ]);
+        ->toBe($dataStructure);
 });
 
 it('validates that the ValidatedDTO with nested data can be converted into a JSON string', function () {
-    $validatedDTO = new UserNestedDTO([
+    $dataStructure = [
         'name' => [
             'first_name' => $this->subject_name,
             'last_name' => 'Doe',
         ],
         'email' => $this->subject_email,
-    ]);
+    ];
+    $validatedDTO = new UserNestedDTO($dataStructure);
 
     expect($validatedDTO)->toJson()
-        ->toBe('{"name":{"first_name":"' . $this->subject_name . '","last_name":"Doe"},"email":"' . $this->subject_email . '"}');
+        ->toBe(json_encode($dataStructure));
 });
 
 it('validates that the ValidatedDTO with nested data can be converted into a pretty JSON string', function () {
-    $validatedDTO = new UserNestedDTO([
+    $dataStructure = [
         'name' => [
             'first_name' => $this->subject_name,
             'last_name' => 'Doe',
         ],
         'email' => $this->subject_email,
-    ]);
+    ];
+    $validatedDTO = new UserNestedDTO($dataStructure);
 
     expect($validatedDTO)->toPrettyJson()
-        ->toBe(json_encode(
+        ->toBe(json_encode($dataStructure, JSON_PRETTY_PRINT));
+});
+
+it('validates that the ValidatedDTO with nested collection data can be converted into an array', function () {
+    $dataStructure = [
+        'names' => [
             [
-                'name' => [
-                    'first_name' => $this->subject_name,
-                    'last_name' => 'Doe',
-                ],
-                'email' => $this->subject_email,
+                'first_name' => $this->subject_name,
+                'last_name' => 'Doe',
+            ],
+            [
+                'first_name' => 'Jane',
+                'last_name' => 'Doe',
             ],
-            JSON_PRETTY_PRINT
-        ));
+        ],
+        'email' => $this->subject_email,
+    ];
+    $validatedDTO = new UserNestedCollectionDTO($dataStructure);
+
+    expect($validatedDTO)->toArray()
+        ->toBe($dataStructure);
+});
+
+it('validates that the ValidatedDTO with nested collection data can be converted into a JSON string', function () {
+    $dataStructure = [
+        'names' => [
+            [
+                'first_name' => $this->subject_name,
+                'last_name' => 'Doe',
+            ],
+            [
+                'first_name' => 'Jane',
+                'last_name' => 'Doe',
+            ],
+        ],
+        'email' => $this->subject_email,
+    ];
+    $validatedDTO = new UserNestedCollectionDTO($dataStructure);
+
+    expect($validatedDTO)->toJson()
+        ->toBe(json_encode($dataStructure));
+});
+
+it('validates that the ValidatedDTO with nested collection data can be converted into a pretty JSON string', function () {
+    $dataStructure = [
+        'names' => [
+            [
+                'first_name' => $this->subject_name,
+                'last_name' => 'Doe',
+            ],
+            [
+                'first_name' => 'Jane',
+                'last_name' => 'Doe',
+            ],
+        ],
+        'email' => $this->subject_email,
+    ];
+    $validatedDTO = new UserNestedCollectionDTO($dataStructure);
+
+    expect($validatedDTO)->toPrettyJson()
+        ->toBe(json_encode($dataStructure, JSON_PRETTY_PRINT));
 });
 
 it('validates that the ValidatedDTO can be converted into an Eloquent Model', function () {