This study describes the preparation, characterization and evaluation of performance and antifouling properties of mixed matrix nanofiltration membranes. The membranes were prepared by acid oxidized multiwalled carbon nanotubes (MWCNTs) embedded in polyethersulfone as matrix polymer. The hydrophilicity of the membrane was enhanced by blending MWCNTs due to migration of functionalized MWCNTs to membrane surface during the phase inversion process. The morphology studies of the prepared NF membranes by scanning electron microscopy (SEM) showed that very large macro-voids appeared in sub-layer by addition of low amount of functionalized MWCNT leading to increase of pure water flux. By using the proper amount of modified MWCNTs, it was possible to increase both the flux and the salt rejection of the membranes. In this work, the effect of CNT/polymer membrane for fouling minimization is presented. The antifouling performance of membranes fouled by bovine serum albumin (BSA) was characterized by means of measuring the pure water flux recovery. The results indicate that the surface roughness of membranes play an important role in antibiofouling resistance of MWCNT membranes. The membrane with lower roughness (0.04 wt% MWCNT/PES) represented the superior antifouling property. The salt retention by the negatively charged MWCNT embedded membrane indicated Donnan exclusion mechanism. The salt retention sequence for 0.04 wt% MWCNT was Na2SO4 (75%) > MgSO4 (42%) > NaCl (17%) after 60 min filtration. (C) 2011 Elsevier B.V. All rights reserved.