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.
