This paper proposes a decentralized output feedback control scheme applied to two-area interconnected power system. The controller synthesis problem is formulated as the scaled ℋ∞ control problem and a new LMI-based algorithm is proposed to compute the decentralized controller. The proposed controller is robust with regard to parametric uncertainties and also attenuates bounded exogenous disturbances in the sense of L2-gain. Simulation results clearly show the effectiveness of the developed decentralized output feedback control scheme.