A medicament injection device comprising a main body configured to receive a medicament cartridge sealed by a first penetrable barrier a cap assembly comprising a button cap and a carrier unit, the button cap being rotatable with respect to the carrier unit and wherein the button cap is prevented from being displaced axially in a proximal direction unless the button is rotated into alignment with respect to the carrier unit, a needle carrier releasably coupled to the carrier unit, the needle carrier carrying a needle having a proximal end and a distal end, the needle carrier being releasably coupled to the push button, wherein, subsequent to rotational alignment of the button cap with respect to the carrier unit, the button cap is axially displaceable in the proximal direction, wherein axial displacement of the button cap in the proximal direction causes the needle carrier to be displaced axially in the proximal direction and wherein, subsequent to axial displacement of the button cap in the proximal direction, the cap assembly is separable from the main body in a distal direction.
