An attachment device for attaching a component to a support component, in particular a support component of a vehicle, includes a retaining element which can be inserted into an opening of the support component and which has a latching feature for releasably latching to the opening of the support component. A locking element can be inserted into the retaining element, wherein, when the locking element is inserted into the retaining element, the latching feature of the retaining element is/are blocked so as to prevent release of the latching. The retaining element has a sealing ring for bearing in a sealing manner against the opening of the support component, which sealing ring, when inserted into the opening of the support component, bears in a sealing manner against opposite sides of the support component.