The invention relates to an activating mechanism for a medicament delivery device (1), comprising: —an outer body (8), —a cartridge (2) containing a dosage of a medicament and sealed with a sealing element (2.1) that is arranged across an open distal end of the cartridge (2), —a cartridge carrier (4) adapted to hold the cartridge (2), —a needle safety mechanism adapted to hold a double-ended hollow needle (6) and to relatively move along a longitudinal axis (L) with respect to the cartridge (2) and to the outer body (8) to cover or to expose the needle (6), —wherein in an initial position (P1) of the medicament delivery device (1), the double-ended hollow needle (6) is spaced from the cartridge (2) in a distal direction (D), and —wherein when the needle safety mechanism is pressed into the outer body (8), a proximal end of the needle (6) pierces the sealing element (2.1). The invention further relates to a medicament delivery device (1) comprising such an activating mechanism.
