The aim of this study was developing novel membranes based on polyethersulfone (PES) as matrix and amine functionalized cellulose nanocrystals (CNC) as nanofiller for copper ion and direct red-16 removal from water. The surface modification of CNC was performed using (3-aminopropyl)triethoxysilane (APTES) and confirmed by Fourier transform infrared spectroscopy and energy dispersive X-ray spectroscopy. Then, PES membranes were prepared by embedding various concentrations (0, 0.1, 0.5, and 1 wt%) of modified CNC (MCNC). The results showed that the maximum adsorption capacity of copper ions was 90% for membranes containing 1 wt% MCNC. Dye removal percentage was 89% for neat PES and increased to 99% for 1 wt% MCNC loading. The outcomes of this...