Pneumatic double acting cylinders are able to provide inherent stiffness and force control for compliant motion control applications. Impedance control methods allow for a broad spectrum of mechanical properties of actuators to be achieved. The range of this spectrum can be increased by simultaneously controlling the actuator’s inherent stiffness and impedance, a concept explored in this paper. Presented here is a sliding mode impedance and stiffness controller for a servo-pneumatic double acting cylinder. Two proportional servo-valves are employed for simultaneous control of the virtual impedance and inherent stiffness of the pneumatic cylinder. Experimental results of tracking trajectories and contact are reported and discussed with respect to different approaches in the literature.