An injection device, comprising: - a generally elongated tubular housing having opposite proximal and distal ends; - a needle shield sleeve slidably and coaxially arranged inside the housing and protruding a distance outside the proximal end of the housing; - a syringe carrier mechanism comprising a syringe carrier slidably and coaxially arranged to the needle shield sleeve, wherein said syringe carrier comprises a syringe having a medicament and a needle; - a first activator member slidably movable in a distal direction and coaxially arranged to the housing and connected to said needle shield sleeve; - an actuating member slidaby and coaxially arranged to the first activator member; - a drive mechanism slidably and coaxially arranged to the actuating member and to the syringe carrier mechanism, said drive mechanism being controlled by the actuating member and wherein the drive mechanism comprises a plunger rod arranged to act on the syringe and a first compression spring arranged to drive the plunger rod; wherein the actuating member comprises flexible tongues having annular inwardly directed ledges, and the plunger rod comprises a circumferential groove having a mutual shape as that of the ledges so that the ledges fit into the groove, - a second activator member slidably and coaxially arranged to the distal end of the housing and fixedly connected to the actuating member; characterised in that the first activator member has a distal end arranged with at least two oppositely arranged guide members extending in the distal direction, the second activator member has two first tongues, each having a radially inwards extending ledge, and that the first and the second activator members are coaxially movable relative each other from a non-activation position in which the first and the second activator members are abutting to each other and the plunger is held against the force of the first compression spring by the inwardly directed ledges of the tongues, and by the first activator member which surrounds and prevents the tongues from moving radially outwards, to an activation position, and wherein the first and the second activator members are co-acting independent of the sequence in which said activator members are activated, whereby each guide member of the first activator member comes under the proximal end of the respective first tongue of the second activator member and a portion of a band-shaped part of the actuating member with enlarged diameter comes out from the surrounding of the first activator member; and wherein only in the activation position is the actuating member capable of releasing the drive mechanism to move said syringe carrier mechanism for penetrating the needle and to deliver said medicament through the needle. - a generally elongated tubular housing having opposite proximal and distal ends; - a needle shield sleeve slidably and coaxially arranged inside the housing and protruding a distance outside the proximal end of the housing; - a syringe carrier mechanism comprising a syringe carrier slidably and coaxially arranged to the needle shield sleeve, wherein said syringe carrier comprises a syringe having a medicament and a needle; - a first activator member slidably movable in a distal direction and coaxially arranged to the housing and connected to said needle shield sleeve; - an actuating member slidaby and coaxially arranged to the first activator member; - a drive mechanism slidably and coaxially arranged to the actuating member and to the syringe carrier mechanism, said drive mechanism being controlled by the actuating member and wherein the drive mechanism comprises a plunger rod arranged to act on the syringe and a first compression spring arranged to drive the plunger rod; wherein the actuating member comprises flexible tongues having annular inwardly directed ledges, and the plunger rod comprises a circumferential groove having a mutual shape as that of the ledges so that the ledges fit into the groove, - a second activator member slidably and coaxially arranged to the distal end of the housing and fixedly connected to the actuating member; characterised in that the first activator member has a distal end arranged with at least two oppositely arranged guide members extending in the distal direction, the second activator member has two first tongues, each having a radially inwards extending ledge, and that the first and the second activator members are coaxially movable relative each other from a non-activation position in which the first and the second activator members are abutting to each other and the plunger is held against the force of the first compression spring by the inwardly directed ledges of the tongues, and by the first activator member which surrounds and prevents the tongues from moving radially outwards, to an activation position, and wherein the first and the second activator members are co-acting independent of the sequence in which said activator members are activated, whereby each guide member of the first activator member comes under the proximal end of the respective first tongue of the second activator member and a portion of a band-shaped part of the actuating member with enlarged diameter comes out from the surrounding of the first activator member; and wherein only in the activation position is the actuating member capable of releasing the drive mechanism to move said syringe carrier mechanism for penetrating the needle and to deliver said medicament through the needle.