An attachment for an electric toothbrush, including a working head and coupling member mountable on a toothbrush handpiece. The coupling member includes a sleeve-shaped coupling insert with an engagement section for locking with the handpiece. The coupling insert is displaceable relative to the coupling member or an actuating member such that an axial movement of the coupling insert relative to the coupling member or actuating member produces an unlocking/locking movement of the engagement section in a direction transverse to the attachment longitudinal direction. The attachment or actuating member is first moved axially relative to a locked coupling insert until the axial relative movement releases the lock for the coupling insert and the attachment to be separated from the toothbrush handpiece. This two-stage attaching or connecting mechanism permits use of non-self-locking connecting or faying contours because the locking movement takes place in a direction transverse to the attachment longitudinal direction.