In this study, cavity pressure control of a computer controlled powder injection moulding setup driven by an electro-hydraulic servovalve was investigated both theoretically and experimentally. For this purpose, a detailed system model of a powder injection moulding machine was developed and the important parameters that affect the system behaviour were determined by carrying out computer simulations. In light of the simulation results, a closed-loop control system was designed and manufactured. The control system was implemented to a specially designed powder injection moulding setup. Comparisons of the theoretical and experimental results demonstrate that the developed system model describes the dynamic behaviour of the system satisfactorily. The results of experiments show that accurate control of the cavity pressure can be achieved by the proposed control system.