ABSTRACT In this work, the potential of peach pit biosorption in the removal of the drug metformin hydrochloride from water is evaluated. Experiments are carried out in a closed batch system to evaluate the effect of the solution pH (2–10), temperature (25, 35 and 45 °C), stirring (100, 150 and 200 rpm) and chemical treatments. During the study, biosorbent characterization, kinetic tests, equilibrium tests and thermodynamic parameter calculations are performed. The operating conditions that show the best results for both the raw biosorbent and the biosorbent submitted to acid, basic and acid followed by basic treatments with removal capacities of 3.17, 10.83, 18.10 and 49.14 mg g−1, respectively, are pH 7, 25 °C and 100 rpm, which result in an equilibrium time of 12 h. In the kinetic study, the pseudo-second-order model represents the best fit for the experimental data, while the Langmuir model best represents the equilibrium data. The biomasses submitted to chemical treatments show a significant increase in drug removal capacity related to the raw biosorbent, with the best maximum absorption of 82.54±1.34 mg g−1 achieved after the application of the acid followed by basic treatment. These results show that peach pit has potential to be used as a low-cost biosorbent to remove drugs from water.