A robust auxiliary wide area damping controller is proposed for a unified power flow controller (UPFC). The mixed H 2 / H ∞ problem with regional pole placement, resolved by linear matrix inequality (LMI), is applied for controller design. Based on modal analysis, the optimal wide area input signals for the controller are selected. The time delay of input signals, due to electrical distance from the UPFC location is taken into account in the design procedure. The proposed controller is applied to a multi-machine interconnected power system from the IRAN power grid. It is shown that the both transient and dynamic stability are significantly improved despite different disturbances and loading conditions.