diff --git a/tests/Fixtures/ThreadMessage.php b/tests/Fixtures/ThreadMessage.php
new file mode 100644
index 00000000..5e9e4d29
--- /dev/null
+++ b/tests/Fixtures/ThreadMessage.php
@@ -0,0 +1,60 @@
+<?php
+
+/**
+ * @return array<string, mixed>
+ */
+function threadMessageResource(): array
+{
+    return [
+        'id' => 'msg_KNsDDwE41BUAHhcPNpDkdHWZ',
+        'object' => 'thread.message',
+        'created_at' => 1699623839,
+        'thread_id' => 'thread_agvtHUGezjTCt4SKgQg0NJ2Y',
+        'role' => 'user',
+        'content' => [
+            [
+                'type' => 'text',
+                'text' => [
+                    'value' => 'How does AI work? Explain it in simple terms.',
+                    'annotations' => [
+                    ],
+                ],
+            ],
+        ],
+        'file_ids' => [
+            'file-DhxjnFCaSHc4ZELRGKwTMFtI',
+        ],
+        'assistant_id' => null,
+        'run_id' => null,
+        'metadata' => [],
+    ];
+}
+
+/**
+ * @return array<string, mixed>
+ */
+function threadMessageListResource(): array
+{
+    return [
+        'object' => 'list',
+        'data' => [
+            threadMessageResource(),
+            threadMessageResource(),
+        ],
+        'first_id' => 'msg_KNsDDwE41BUAHhcPNpDkdHWZ',
+        'last_id' => 'msg_KNsDDwE41BUAHhcPNpDkdHWZ',
+        'has_more' => false,
+    ];
+}
+
+/**
+ * @return array<string, mixed>
+ */
+function threadMessageDeleteResource(): array
+{
+    return [
+        'id' => 'msg_KNsDDwE41BUAHhcPNpDkdHWZ',
+        'object' => 'thread.message.deleted',
+        'deleted' => true,
+    ];
+}
diff --git a/tests/Resources/ThreadsMessages.php b/tests/Resources/ThreadsMessages.php
new file mode 100644
index 00000000..ac241260
--- /dev/null
+++ b/tests/Resources/ThreadsMessages.php
@@ -0,0 +1,139 @@
+<?php
+
+use OpenAI\Responses\Meta\MetaInformation;
+use OpenAI\Responses\Threads\Messages\ThreadMessageDeleteResponse;
+use OpenAI\Responses\Threads\Messages\ThreadMessageListResponse;
+use OpenAI\Responses\Threads\Messages\ThreadMessageResponse;
+use OpenAI\Responses\Threads\Messages\ThreadMessageResponseContentTextObject;
+use OpenAI\ValueObjects\Transporter\Response;
+
+test('list', function () {
+    $client = mockClient('GET', 'threads/thread_agvtHUGezjTCt4SKgQg0NJ2Y/messages', [], Response::from(threadMessageListResource(), metaHeaders()));
+
+    $result = $client->threads()->messages()->list('thread_agvtHUGezjTCt4SKgQg0NJ2Y');
+
+    expect($result)
+        ->toBeInstanceOf(ThreadMessageListResponse::class)
+        ->object->toBe('list')
+        ->data->toBeArray()->toHaveCount(2)
+        ->data->each->toBeInstanceOf(ThreadMessageResponse::class)
+        ->firstId->toBe('msg_KNsDDwE41BUAHhcPNpDkdHWZ')
+        ->lastId->toBe('msg_KNsDDwE41BUAHhcPNpDkdHWZ')
+        ->hasMore->toBeFalse();
+
+    expect($result->meta())
+        ->toBeInstanceOf(MetaInformation::class);
+});
+
+test('create', function () {
+    $client = mockClient('POST', 'threads/thread_agvtHUGezjTCt4SKgQg0NJ2Y/messages', [
+        'role' => 'user',
+        'content' => 'How does AI work? Explain it in simple terms.',
+        'file_ids' => [
+            'file-DhxjnFCaSHc4ZELRGKwTMFtI',
+        ],
+    ], Response::from(threadMessageResource(), metaHeaders()));
+
+    $result = $client->threads()->messages()->create('thread_agvtHUGezjTCt4SKgQg0NJ2Y', [
+        'role' => 'user',
+        'content' => 'How does AI work? Explain it in simple terms.',
+        'file_ids' => [
+            'file-DhxjnFCaSHc4ZELRGKwTMFtI',
+        ],
+    ]);
+
+    expect($result)
+        ->toBeInstanceOf(ThreadMessageResponse::class)
+        ->id->toBe('msg_KNsDDwE41BUAHhcPNpDkdHWZ')
+        ->object->toBe('thread.message')
+        ->createdAt->toBe(1699623839)
+        ->threadId->toBe('thread_agvtHUGezjTCt4SKgQg0NJ2Y')
+        ->role->toBe('user')
+        ->content->toBeArray()
+        ->content->toHaveCount(1)
+        ->content->each->toBeInstanceOf(ThreadMessageResponseContentTextObject::class)
+        ->fileIds->toBeArray()
+        ->fileIds->toBe(['file-DhxjnFCaSHc4ZELRGKwTMFtI'])
+        ->assistantId->toBeNull()
+        ->runId->toBeNull()
+        ->metadata->toBeArray()
+        ->metadata->toBeEmpty();
+
+    expect($result->meta())
+        ->toBeInstanceOf(MetaInformation::class);
+});
+
+test('modify', function () {
+    $client = mockClient('POST', 'threads/thread_agvtHUGezjTCt4SKgQg0NJ2Y/messages/msg_KNsDDwE41BUAHhcPNpDkdHWZ', [
+        'metadata' => [
+            'name' => 'My new message name',
+        ],
+    ], Response::from(threadMessageResource(), metaHeaders()));
+
+    $result = $client->threads()->messages()->modify('thread_agvtHUGezjTCt4SKgQg0NJ2Y', 'msg_KNsDDwE41BUAHhcPNpDkdHWZ', [
+        'metadata' => [
+            'name' => 'My new message name',
+        ],
+    ]);
+
+    expect($result)
+        ->toBeInstanceOf(ThreadMessageResponse::class)
+        ->id->toBe('msg_KNsDDwE41BUAHhcPNpDkdHWZ')
+        ->object->toBe('thread.message')
+        ->createdAt->toBe(1699623839)
+        ->threadId->toBe('thread_agvtHUGezjTCt4SKgQg0NJ2Y')
+        ->role->toBe('user')
+        ->content->toBeArray()
+        ->content->toHaveCount(1)
+        ->content->each->toBeInstanceOf(ThreadMessageResponseContentTextObject::class)
+        ->fileIds->toBeArray()
+        ->fileIds->toBe(['file-DhxjnFCaSHc4ZELRGKwTMFtI'])
+        ->assistantId->toBeNull()
+        ->runId->toBeNull()
+        ->metadata->toBeArray()
+        ->metadata->toBeEmpty();
+
+    expect($result->meta())
+        ->toBeInstanceOf(MetaInformation::class);
+});
+
+test('retrieve', function () {
+    $client = mockClient('GET', 'threads/thread_agvtHUGezjTCt4SKgQg0NJ2Y/messages/msg_KNsDDwE41BUAHhcPNpDkdHWZ', [], Response::from(threadMessageResource(), metaHeaders()));
+
+    $result = $client->threads()->messages()->retrieve('thread_agvtHUGezjTCt4SKgQg0NJ2Y', 'msg_KNsDDwE41BUAHhcPNpDkdHWZ');
+
+    expect($result)
+        ->toBeInstanceOf(ThreadMessageResponse::class)
+        ->id->toBe('msg_KNsDDwE41BUAHhcPNpDkdHWZ')
+        ->object->toBe('thread.message')
+        ->createdAt->toBe(1699623839)
+        ->threadId->toBe('thread_agvtHUGezjTCt4SKgQg0NJ2Y')
+        ->role->toBe('user')
+        ->content->toBeArray()
+        ->content->toHaveCount(1)
+        ->content->each->toBeInstanceOf(ThreadMessageResponseContentTextObject::class)
+        ->fileIds->toBeArray()
+        ->fileIds->toBe(['file-DhxjnFCaSHc4ZELRGKwTMFtI'])
+        ->assistantId->toBeNull()
+        ->runId->toBeNull()
+        ->metadata->toBeArray()
+        ->metadata->toBeEmpty();
+
+    expect($result->meta())
+        ->toBeInstanceOf(MetaInformation::class);
+});
+
+test('delete', function () {
+    $client = mockClient('DELETE', 'threads/thread_agvtHUGezjTCt4SKgQg0NJ2Y/messages/msg_KNsDDwE41BUAHhcPNpDkdHWZ', [], Response::from(threadMessageDeleteResource(), metaHeaders()));
+
+    $result = $client->threads()->messages()->delete('thread_agvtHUGezjTCt4SKgQg0NJ2Y', 'msg_KNsDDwE41BUAHhcPNpDkdHWZ');
+
+    expect($result)
+        ->toBeInstanceOf(ThreadMessageDeleteResponse::class)
+        ->id->toBe('msg_KNsDDwE41BUAHhcPNpDkdHWZ')
+        ->object->toBe('thread.message.deleted')
+        ->deleted->toBe(true);
+
+    expect($result->meta())
+        ->toBeInstanceOf(MetaInformation::class);
+});