Polyethersulfone ultrafiltration membranes prepared via immersion precipitation were modified by TiO₂ nanoparticles and UV irradiation. Three sets of membranes, i.e. TiO₂-entrapped membranes, UV-irradiated TiO₂-entrapped membranes and UV-irradiated TiO₂-deposited membranes were prepared. The membranes were characterized by contact angle, SEM, FTIR, cross-flow filtration (pure water flux and milk water permeation) and antifouling measurements. The initial flux of TiO₂-entrapped membrane was lower than the initial flux of neat PES membrane. However, the former membrane showed lower flux decline compared to the neat PES membrane. UV-irradiated TiO₂-entrapped membranes represented higher flux and higher antifouling properties compared to TiO₂-entrapped membranes. Contact angle measurement, FTIR and surface SEM image indicate that the TiO₂ nanoparticles uniformly settled on the membrane surface by dipping the membrane into the TiO₂ colloidal suspension. Flux behavior of 0.03wt.% UV-irradiated TiO₂-deposited membrane indicated higher performance and antifouling properties. TiO₂ colloidal suspension with 0.03wt.%, 15min immersion and 15min UV irradiation with 160W lamp were determined as the optimum conditions for modification of PES membrane. Finally, a comparison between UV-irradiated TiO₂-entrapped and deposited membranes proved that coating TiO₂ on membrane surface is a superior technique for the modification of PES membranes to minimize membrane fouling.