An assembly for a counter mechanism for a drug delivery device is described comprising a drive member, wherein the drive member is adapted and arranged to be rotated in a first rotational direction and to be prevented from rotation in a second rotational direction which direction is opposite to the first rotational direction, an advancing member adapted and arranged to be axially moved and rotated with respect to the drive member, wherein the advancing member is adapted and arranged to mechanically cooperate with the drive member such that the drive member is rotated in the first rotational direction, and a display member which is configured to count a number of doses and to display the counted number of doses, wherein the assembly is adapted and arranged such that rotation of the drive member in the first rotational direction is converted into a counting movement of the display member. Furthermore, a drug delivery device comprising the assembly is described.
