This study explores the feasibility of pre-treated coffee waste (PCW) as biosorbent for the removal of diazinon. The effect of the pesticide concentration (6-20 mg), solution pH (3-11.5), temperature (15-40°C) and co-existing inorganic ions (H 2 PO 4 -, NO 3 -) on the diazinon biosorption over PCW is investigated. The experimental results indicate an optimal pH of 7.3 for the diazinon elimination on PCW (1 g L -1 ). The Langmuir model describes well the isotherm data with a high regression coefficient (R 2 [ 0.990) and a maximum monolayer biosorption capacity of 18.52 mg g -1 at 15°C. It is also observed that the intra-particle diffusion is not the rate-controlling step. A comparison is evaluated between the pseudo-second-order and intra-particle diffusion kinetic models; the experimental data are well fitted by the pseudosecond-order kinetic model. The biosorption capacity decreases with increasing temperature for a diazinon concentration of 10 mg L -1 . The negative enthalpy DH°( -63.57 kJ/mol) indicates that the diazinon biosorption onto PCW is exothermic. Under optimal conditions, the biosorption reaches 95% after 90 min. The removal efficiency decreases from 95 to 65.67 and 48.9% for the diazinon alone and in the presence of NO 3 -and H 2 PO 4 -(100 mg L -1 ), respectively.