© 2020, Turkish Chemical Society. All rights reserved.In this study, a novel, low-cost, natural, and highly effective adsorbent, chitosan (Ch)-diatomite (D) composite was synthesized. Ch-D composite was tested as an effective and alternative adsorbent for the removal of Pb2+ ions. The Ch-D composite was characterized by FT-IR, SEM-EDX and PZC analyses. The adsorption process of Pb2+ ions onto Ch-D as initial lead concentration, solution pH, temperature, contact time and recovery was investigated. From the adsorption process results, it has been observed that the highest removal efficiency is approximately 95% at a contact time of 4-hour, initial Pb2+ concentration of 500 mg L-1 and agitation speed of 150 rpm at natural pH 4.0. The maximum Pb2+ adsorption capacity from the Langmuir model was found as 0.154 mol kg-1 at 25°C. Besides, adsorption kinetics was also explained with pseudo-first-order models. Adsorption thermodynamics have shown that Pb2+ adsorption onto Ch-D is possible, spontaneous and exothermic. Ch-D composite can become an alternative adsorbent for the treatment of lead ions in the wastewater.