A drug delivery device comprises a shield (30) moveably mounted to a main portion and being displaceable by a user between a shielding and a non-shielding position, wherein a needle assembly (50) can be mounted on a reservoir, the shield covering the needle assembly in the shielding position. The needle assembly is moveable between a dis-connected and connected position in fluid communication with the reservoir. In such an arrangement a mounted needle assembly is moved from the dis-connected to the connected position when the shield is moved from the shielding to the non-shielding position, and moved from the connected to the dis-connected position when the shield is moved from the non-shielding to the shielding position.