Biodegradable cellulose acetate (CA) membranes were prepared via phase inversion induced by immersion precipitation method. Acetic acid and deionized water were used as solvent and non-solvent, respectively. The modifying effect of gelatin and zinc oxide (ZnO) nanoparticles additives was investigated on the membranes in terms of water flux, protein rejection percentage, and fouling ability during two hours of bovine serum albumin separation from aqueous solution. Specimens were characterized by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), tensile test, contact angle technique, and porosity measurement. The incorporation of gelatin and ZnO nanoparticles into the CA matrix increased the porosity coefficient and hydrophilicity. Moreover, gelatin improved the tensile properties of the membrane.