In the current research, poly(phenylene ether-ether sulfone) (PEES)-co-poly vinyl pyrrolidone (PVP) nanofiltration membranes were prepared by a casting solution technique using N-methyl-2-pyrrolidone (NMP) as a solvent. The ethanol was used as fixed additive for better dispersion of iron oxide nanoparticles into the membranes structure. The effect of iron oxide nanoparticle concentration in the casting solution on the membrane performance/properties was studied. The membrane pure water flux, permeated flux, salt rejection, water content, tensile strength and membrane porosity were studied. Scanning electron microscopy (SEM) analysis was also used for the membrane morphology characterization. The results revealed that water content increased from 70.25% for bare PEES to about 83.25% for the membrane filled with 0.05 wt.% nanoparticles. SEM images showed that the membrane structure changed and turned from sponge shape to finger like. The results showed that porosity was increased from 55.92% for PEES one to 69.65% for M3. Additionally, the maximum value of flux was obtained for M3. Moreover, rejection was improved by the addition of nanoparticles into the casting solution compared to the unfilled one. Obtained results showed more appropriate performance for the modified membrane filled with 0.05 wt.% iron oxide nanoparticles compared to other prepared membranes.