The decolourisation of C.I. basic yellow1 in aqueousmediumwas studied using a 25W low-pressure ultra-violet (UV) lamp along with H2O2 as an oxidant. It was observed that when H2O2 was used with UV radiation, the decolourisation rate became faster and 98.1% of colour removal was occurred in 20min at 20mg/L of initial dye concentration. Itwas also observed that decolourisation is dependent on initial concentration of H2O2, initial concentration of dye solution, UV dosage and pH. The decolourisation rate followed pseudo-first order kinetics with respect to the dye concentration.