This paper presents efforts to design and test the efficacy of ‘PSO-PID’ controller tuning and investigate the impact of different objective functions on the performance of single and two-area power systems. For the single-area power system, the performance of ‘Ziegler-Nichols PID (ZN-PID)’ tuning is compared with ‘Particle Swarm Optimization PID (PSO-PID)’ tuning. Results show that PSO-PID significantly simplifies calculations for higher-order plants and effectively minimizes oscillations, resulting in a reduced settling time. In the two-area power system, PSO-PID controllers are evaluated using different objective functions like ‘Integral of Absolute Error (IAE), Integral of Time-weighted Absolute Error (ITAE), Integral of Squared Error (ISE) and Integral of Time-weighted Squared Error (ITSE).’ MATLAB simulation results show that the ISE objective function yields superior closed loop performance in terms of output frequency variation for area-1, while the IAE objective function excels for area-2. Both ISE and IAE functions demonstrate strong overall closed loop performance, with the IAE function providing the least turbine mechanical power variation and minimizing tie-line power variations.