The invention relates to an auto-injector for administering a dose of a liquid medicament, comprising: an elongate housing arranged to contain a syringe with a hollow needle and a stopper for sealing the syringe and displacing the medicament, wherein the syringe is slidably arranged with respect to the housing, spring means capable of, upon activation: pushing the needle from a covered position inside the housing into an advanced position through the orifice and past the proximal end, operating the syringe to supply the dose of medicament, and retracting the syringe with the needle into the covered position after delivering the medicament, activating means. The spring means is a single drive spring arranged to be grounded at a distal end in the housing for advancing the needle and for injecting the dose of medicament via a plunger. The drive spring has its ground in the housing switched to its proximal end for retracting the syringe. An interlock sleeve is telescoped in the proximal end of the housing. The activating means comprises a trigger button arranged at the distal end of the auto-injector, wherein the trigger button is locked, thereby preventing actuation when the interlock sleeve is in its proximal position in an as delivered state and wherein translation of the interlock sleeve unlocks the trigger button so as to allow actuation.