The present invention concerns an assembly for a drug delivery device (1) comprising a drive assembly (3) and a cartridge holder (41). The drive assembly (3) comprises a first engagement member (43) and the cartridge holder (41) comprises a second engagement member (44). The drive assembly (3) is configured to be arranged inside a body (2) of the drug delivery device (1). The drive assembly (3) is engageable to the cartridge holder (41) by an engagement of the first and the second engagement member (43, 44). Moreover, the present invention concerns a method for assembling the drug delivery device (1).
