<p>This study aims to develop a new strategy for surface functionalization of polyethersulfone ultrafiltration membrane using partly bio-based aryl diazonium salts. The combination of diazonium-induced grafting, UV photografting, and bio-based compounds offers a promising strategy for the design of partly bio-based functionalized PES membranes. The first functionalized membrane M1 is prepared by grafting aryl radicals generated via the chemical reduction of partly bio-based aryl diazonium salts derived from 10-undecenoic acid onto the commercial membrane HFK-131. The second functionalized membrane M2 is obtained by combining this initial grafting of partly bio-based aryl radicals with a subsequent UV photografting of undecanoic acid radicals derived from bio-based 10-undeceneoic acid. Both functionalized membranes were characterized using ATR-FTIR spectroscopy, electrochemical impedance spectroscopy, contact angle measurements, and zeta potential analysis. The results reveal significant alterations in transport properties after functionalization. Moreover, both membranes M1 and M2 show significant improvement in the rejection of model charged molecules of antibiotics and dyes in water. A slight improvement in antifouling performance is observed for membrane M2. The amenability of the modification strategy could possibly be transposed to various types of membranes and can target molecules of environmental interests such as antibiotics, dyes, and pesticides.</p>