A needle-free injection device including an outer housing and an inner housing configured to receive a needle-free syringe in one end. The inner housing of the device is moveable within the outer housing between a syringe loading position and a firing position. The device also includes an activation button and a housing lock engaged by the activation button to prohibit movement of the inner housing from the syringe loading position to the firing position if the activation button is activated in the syringe loading position.
