Polyethersulfone (PES) based nanocomposite nanofiltration membrane was prepared by immersion precipitation method and casting solution technique using  poly (acrylic acid) grafted-iron oxide nanoparticles (Fe3O4) as hydrophilic filler additives. For this purpose, iron oxide nanoparticles were modified by in situ polymerization of acrylic acid in aqueous solution by potassium persulfate as initiator and ethylene glycol as cross-linker. The grafted iron oxide nanoparticles were investigated by Fourier transforms infrared spectroscopy. The effect of different concentrations of grafted nanoparticles on the PES nanofiltration membrane performance and properties was investigated by scanning electron microscopy, water content, pure water flux, pore size, permeability flux, rejection and tensile strength. The water content was enhanced by incorporation of nanoparticles into the membrane matrix from 72.04 to 74.75%. It was observed that pure water flux (2.68 to 8.71 L/m2.h), mean pore size (2 to 6 nm) and permeability flux (0.8 to 4 L/m2.h) improved with loading of nanoparticles into the membrane matrix. The results revealed that utilization of grafted iron oxide nanoparticles in the membrane matrix led to improvement of rejection from 53.98 to 89.19% for membrane filled with 0.05% wt. nanoparticles. Also tensile strength increased slightly for sample 1 from 3874 to 4825 kPa for sample 4. Moreover, results showed more appreciation performance for the modified membrane containing PAA-Fe3O4 composite nanofillers compared to membrane filled with bare Fe3O4 nanoparticles.