: This paper presents an effective approach for improving power quality in transmission lines using a UnifiedPowerQuality Conditioner (UPQC) controlled through a fuzzy logic-based technique. Power quality problems suchas voltagesag,voltage swell, harmonics, and supply interruptions can adversely affect sensitive electrical loads and reduce the overall reliabilityof the power system. To overcome these issues, the proposed UPQC system combines both series and shunt active powerfilters,allowing simultaneous compensation of voltage and current disturbances and thereby improving overall systemperformance. In the proposed method, fuzzy logic control is used to continuously regulate the UPQC operating parameters accordingtorealtime system conditions. This adaptive control approach enables the system to respond efficiently under different fault anddisturbance conditions occurring in the transmission network. The complete UPQC model and control strategy are developedandsimulated in MATLAB/Simulink environment. A detailed simulation study is carried out to analyse the performance of the fuzzy logic-based UPQC under various fault scenariosin the transmission line. The obtained results show considerable improvement in power quality parameters, confirmingtheeffectiveness of the proposed control strategy in mitigating disturbances. Overall, the proposed fuzzy logic-based UPQCprovidesareliable and efficient solution for enhancing power quality and maintaining stable operation of transmissionsystemsunderdifferent operating and fault conditions. Keywords: UPQC, MATLAB/Simulink, Line fault, fuzzy logic controller, Harmonics,