This research work investigated the usage of pre-seeding interfacial polymerization method using iron oxide (FeO) nanoparticles on the polyethersulfone (PES) support membrane for water treatment. The two different concentrations (low (0.05 wt%) and high (2 wt%) of FeO nanoparticles were used as the membrane surface modification parameter. Surface modified membranes were characterized by several characterizations methods. Membrane surface charge was calculated qualitatively by using Grahame equation with the help of contact angle measurements. Synthesized membranes showed 90% rejection with polyethylene glycol (PEG) with M.W. 1500 Da, which was fitted in the range of nanofiltration. The membrane performance towards salt rejection, flux (at different pressure) and anti-fouling activity was evaluated using a various salt solution like CaCl2, MgCl2, C6H5Na3O7, Na2SO4, NaCl with an initial concentration of 2000 mg/L, saltwater (collected from Suvali beach, Surat, India). With the increase in the concentration of FeO nanoparticles, hydrophilic nature (84.7 to 49.6 degrees), surface charge (-6.27 to -14.21 mC/m(2)) and flux (27.46 to 36.85 L/m(2)h) of the nanocomposite membranes were effectively enhanced, and also showed the high salt rejections (> 90%). Anti-fouling activity of the membrane with saltwater was analyzed by flux recovery ratio that showed FeO nanoparticles embedded membrane notably reduced the fouling.