This paper presents the stability enhancement mechanisms for power transmission system through the application of a developed model of Unified Power Flow Controller (UPFC). The UPFC model was applied to the existing 5-buses South-South region of Nigerian 330 KV transmission network model while considering it effects on bus voltages and power losses. Simscape Electrical-Specialized Power Systems Toolbox (SESPST) in MATLAB Software was employed for the simulation. The simulation results showed that with incorporation of the controller into the network, about 100% of bus voltages were controlled within acceptable operational range and there was drastic reduction in the overall power losses of the system. The UPFC offers improvement of bus voltages and reduces power losses in the network leading to an enhanced power system stability for the regional network under study.