The present invention relates to a medicament delivery device that comprises an elongated housing; a medicament container carrier adapted to house a medicament container to which a medicament delivery member is attached and wherein the carrier is slidably accommodated within the housing; a trigger unit; a cover unit coaxially and slidably arranged within the housing; a release mechanism adapted to be partly actuated by the operation of the trigger unit and partly actuated by the movement of the cover unit; a preloaded drive unit releasably connected to the medicament container carrier and controlled by the release mechanism for advancing firstly the medicament container carrier to a predetermined proximal position in relation to the housing and upon the carrier reaching the predetermined proximal position, the drive unit becomes disconnected from the carrier for advancing a slidable stopper within the container and thereby dispensing the medicament; and a braking mechanism acting between the preloaded drive unit and the release mechanism for controlling the speed of the preloaded drive unit when advancing the slidable stopper within the container.