In this study, new type of polysulfone (PSI) composite ultrafiltration membranes were prepared by blending PSf with poly[2,2'-(m-phenylene)-5,5'-dibenzimidazole] (PBI). The prepared membranes were characterized by water contact angle, SEM, FTIR, DSC, TG/DTG and cross-flow filtration techniques. We demonstrated that membrane characteristics such as porosity, hydrophilicity and thermal stability of PSf can be significantly enhanced with the incorporation of PBI. The composite membranes exhibited comparable bovine serum albumin (BSA) retention (69% vs. 36%) and water fluxes (355 vs. 228 L/m(2) h) against pristine PSf membranes. (C) 2014 Elsevier B.V. All rights reserved.