diff --git a/packages/core/test/lib/transports/base.test.ts b/packages/core/test/lib/transports/base.test.ts
index 5e6b504d9f6e..e6f33e20e757 100644
--- a/packages/core/test/lib/transports/base.test.ts
+++ b/packages/core/test/lib/transports/base.test.ts
@@ -23,7 +23,7 @@ const ATTACHMENT_ENVELOPE = createEnvelope<EventEnvelope>(
         length: 20,
         filename: 'test-file.txt',
         content_type: 'text/plain',
-        attachment_type: 'text',
+        attachment_type: 'event.attachment',
       },
       'attachment content',
     ] as AttachmentItem,
diff --git a/packages/types/src/attachment.ts b/packages/types/src/attachment.ts
index 55cc795732ea..da7678d1d8f1 100644
--- a/packages/types/src/attachment.ts
+++ b/packages/types/src/attachment.ts
@@ -1,6 +1,23 @@
+export type AttachmentType =
+  | 'event.attachment'
+  | 'event.minidump'
+  | 'event.applecrashreport'
+  | 'unreal.context'
+  | 'unreal.logs';
+
+/**
+ * An attachment to an event. This is used to upload arbitrary data to Sentry.
+ *
+ * Please take care to not add sensitive information in attachments.
+ *
+ * https://develop.sentry.dev/sdk/envelopes/#attachment
+ */
 export interface Attachment {
   data: string | Uint8Array;
   filename: string;
   contentType?: string;
-  attachmentType?: string;
+  /**
+   * The type of the attachment. Defaults to `event.attachment` if not specified.
+   */
+  attachmentType?: AttachmentType;
 }
diff --git a/packages/types/src/envelope.ts b/packages/types/src/envelope.ts
index fe08ce1962d1..5db39eb65f3e 100644
--- a/packages/types/src/envelope.ts
+++ b/packages/types/src/envelope.ts
@@ -1,3 +1,4 @@
+import type { AttachmentType } from './attachment';
 import type { SerializedCheckIn } from './checkin';
 import type { ClientReport } from './clientreport';
 import type { DsnComponents } from './dsn';
@@ -72,7 +73,7 @@ type AttachmentItemHeaders = {
   length: number;
   filename: string;
   content_type?: string;
-  attachment_type?: string;
+  attachment_type?: AttachmentType;
 };
 type UserFeedbackItemHeaders = { type: 'user_report' };
 type FeedbackItemHeaders = { type: 'feedback' };