diff --git a/.changeset/blue-teeth-report.md b/.changeset/blue-teeth-report.md
new file mode 100644
index 00000000000..042669feb92
--- /dev/null
+++ b/.changeset/blue-teeth-report.md
@@ -0,0 +1,7 @@
+---
+'@clerk/backend': minor
+---
+
+Add `user_id` field to `organizationInvitation.accepted` webhook events.
+
+Creates a new `OrganizationInvitationAcceptedJSON` interface that extends `OrganizationInvitationJSON` with a required `user_id` field, and updates the webhook type system to use this interface specifically for `organizationInvitation`.accepted events.
diff --git a/packages/backend/src/api/resources/JSON.ts b/packages/backend/src/api/resources/JSON.ts
index 91ddd021239..cc67a8c347c 100644
--- a/packages/backend/src/api/resources/JSON.ts
+++ b/packages/backend/src/api/resources/JSON.ts
@@ -392,6 +392,10 @@ export interface OrganizationInvitationJSON extends ClerkResourceJSON {
   expires_at: number;
 }
 
+export interface OrganizationInvitationAcceptedJSON extends OrganizationInvitationJSON {
+  user_id: string;
+}
+
 /**
  * @interface
  */
diff --git a/packages/backend/src/api/resources/Webhooks.ts b/packages/backend/src/api/resources/Webhooks.ts
index b208748f1e3..16b4d0e1e9c 100644
--- a/packages/backend/src/api/resources/Webhooks.ts
+++ b/packages/backend/src/api/resources/Webhooks.ts
@@ -5,6 +5,7 @@ import type {
   DeletedObjectJSON,
   EmailJSON,
   OrganizationDomainJSON,
+  OrganizationInvitationAcceptedJSON,
   OrganizationInvitationJSON,
   OrganizationJSON,
   OrganizationMembershipJSON,
@@ -52,10 +53,15 @@ export type OrganizationMembershipWebhookEvent = Webhook<
 >;
 
 export type OrganizationInvitationWebhookEvent = Webhook<
-  'organizationInvitation.accepted' | 'organizationInvitation.created' | 'organizationInvitation.revoked',
+  'organizationInvitation.created' | 'organizationInvitation.revoked',
   OrganizationInvitationJSON
 >;
 
+export type OrganizationInvitationAcceptedWebhookEvent = Webhook<
+  'organizationInvitation.accepted',
+  OrganizationInvitationAcceptedJSON
+>;
+
 export type RoleWebhookEvent = Webhook<'role.created' | 'role.updated' | 'role.deleted', RoleJSON>;
 
 export type PermissionWebhookEvent = Webhook<
@@ -98,6 +104,7 @@ export type WebhookEvent =
   | OrganizationDomainWebhookEvent
   | OrganizationMembershipWebhookEvent
   | OrganizationInvitationWebhookEvent
+  | OrganizationInvitationAcceptedWebhookEvent
   | RoleWebhookEvent
   | PermissionWebhookEvent
   | WaitlistEntryWebhookEvent