Oil palm shell activated carbon (OPSAC) was investigated for adsorption of 4-chloro-2-methoxyphenol (4C2MP) in aqueous solution. The effects of solution pH, agitation time, and initial concentration were evaluated. Adsorption increased as the contact time increased with the highest adsorption obtained in acidic conditions. The Brunauer-Emmett-Teller (BET) surface area was 1571 m2/g, the total pore volume was 0.8 cm3/g and the average pore diameter was 2.15 nm. Adsorption data were fitted using a Langmuir isotherm, with a maximum monolayer adsorption capacity of 323.62 mg/g. Adsorption kinetics were found to follow a pseudo-second-order model.