An injection device having an outer housing configured to receive a syringe. The syringe has a barrel for containing medicament and a needle in fluid communication with the barrel. The device further has a needle shield axially moveable relative to the outer housing between a needle covering position and a needle exposing position and a biasing means to bias the needle shield axially forwardly toward the needle covering position. A locking sleeve, axially movable relative to the outer housing between a non-locking position and a locking position, selectively limits axial movement of the needle shield. In a first configuration, the needle shield is axially slideable within the locking sleeve to permit rearward axial movement of the needle shield from the needle covering position to the needle exposing position. In a subsequent configuration, the needle shield is prevented from moving axially rearwardly by interference with the locking sleeve, thereby maintaining the needle shield in the needle protecting position. The device may reduce the risk of needle stick injuries when compared to known injection devices and also may prevent unintentional re use of the device.