A medicament delivery device is provided. The medicament delivery device may include, among other features, a cartridge holder mounted in a housing and configured to receive a cartridge containing a medicament. The device may also include an outer cap detachably connected to the housing, and a coupling mechanism configured to connect the outer cap to an injection needle holder to which an injection needle is fixed. The coupling mechanism may include a rotatable member configured to be connected to an injection needle holder. The coupling mechanism may also be threadedly engaged with, and rotatable to, the outer cap. The configuration of the device may allow for quicker and more efficient delivery of medicament.