Abstract: The major power quality issues are voltage sag, voltage swell and voltage harmonics in distribution system. These power quality issues are solved by custom power conditioning devices such as Dynamic Voltage Restorer (DVR), Distributed Static Compensator (DSTATCOM) and Unified Power Quality Conditioner (UPQC). This study presents the ability of Unified Power Quality Conditioner (UPQC) to mitigate voltage sag, voltage swell and voltage harmonics in distribution system. UPQC is modeled in MATLAB-SIMULINK environment with Fuzzy Logic (FL), Neural Network (NN) and Neuro Fuzzy (NF) controllers. The performances of UPQC with three controllers are compared and from comparison it is concluded that UPQC with NF controller effectively mitigates voltage sag, voltage swell and voltage harmonics.