This paper presents a decentralized controller design procedure for inter-area oscillation in power systems. The tuning parameters of the damping controller are computed to assure the stability of the power machines and the synchronization of their rotor angles via some error equations. The key feature is a simple solution without using remote signals from wide-area measurement systems (WAMS), which saves money and complexity in the system analysis due to the time-delay associated to this technology. Simulation results illustrate the viability of the proposed scheme.