© 2020 Elsevier LtdThe effect of erbium (III) molybdate (Er2MoO6) nanomaterial as a new nanofiller on fabrication of polyethersulfone (PES) mixed matrix membranes was examined in terms of membrane morphology, hydrophilicity, permeability, mechanical strength, dye and protein separation and antifouling property. The synthesized Er2MoO6 nanoparticles were characterized by X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy and scanning electron microscopy (SEM). The morphology and surface properties of the prepared nanocomposite membranes were evaluated by SEM images, surface roughness parameters using atomic force microscopy (AFM) and contact angle measurement. The pure water flux of the nanocomposite membranes improved significantly (195.3 L/m2 h at 3 bar for 1 wt.%) after adding of Er2MoO6 due to the higher hydrophilicity in comparison with bare one (82.5 L/m2 h). The fouling resistance results exhibited that 1 wt% Er2MoO6 blended membrane had the best antifouling characteristic (flux recover ratio of 87.6 %). Evaluation of membrane separation performance was performed by examining the Reactive Red 195 rejection. The dye rejection data showed that the Er2MoO6/PES membranes have better dye removal capacity rather than the unfilled PES. It could be say that the Er2MoO6 nanocomposite membranes showed the suitable antibiofouling properties tested by BSA filtration due to low surface roughness and high hydrophilicity prompted by the blended nanomaterial.