The efficiency of sodium hydroxide treated rubber (Hevea brasiliensis) leaves powder (NHBL) for removing copper ions fromaqueous solutions has been investigated. The effects of physicochemical parameters on biosorption capacities such as stirring speed,pH, biosorbent dose, initial concentrations of copper, and ionic strength were studied. The biosorption capacities of NHBL increasedwith increase in pH, stirring speed and copper concentration hut decreased with increase in biosorbent dose and ionic strength. Theisotherm study indicated that NHBL fitted well with Langmuir model compared to Freundlich and Dubinin-Radushkevich models. Themaximum biosorption capacity determined from Langmuir isotherm was 14.97 mg/g at 27~C. The kinetic study revealed that pseudo-second order model fitted well the kinetic data, while Boyd kinetic model indicated that film diffusion was the main rate determiningstep in biosorption process. Based on surface area analysis, NHBL has low surface area and categorized as macroporous. Fouriertransform infrared (FT-IR) analyses revealed that hydroxyl, carboxyl, and amino are the main functional groups involved in the bindingof copper ions. Complexation was one of the main mechanisms for the removal of copper ions as indicated by FT-IR spectra. Ionexchange was another possible mechanism since the ratio of adsorbed cations (Cu2+ and H+) to the released cations (Na, andMg