Removal of hexavalent chromium from aqueous solution was investigated using modified palm shell activated carbon in a batch adsorption system. Polyethylenimine (PEI) is a kind of water-soluble polyamine and it is well known for use to modify adsorbent surface to increase the adsorption capacity. PEI by low molecular weight used for impregnation of palm shell activated carbon. The maximum amount of LMW PEI adsorbed on AC was determined to be approximately 228.2 mg/g carbon. The adsorption experiments were carried out in a batch system using potassium dichromate as the source of chromium (VI) in the synthetic wastewater and modified palm shell activated carbon as the adsorbent. The effects of pH, chromium initial concentration and PEI loading were studied. At pH 3, for the optimum modified sorbent (7.84 mg PEI/g AC) the maximum removal efficiency was 76.64%. The maximum amount of chromium(VI) adsorbed on impregnated activated carbon was determined to be approximately 15.91 mg Cr(VI)/g Ac. The adsorption data conformed well with Langmuir isotherm model.