This study has been conducted on the determination of optimum conditions in treatment of carbofos which one of the organophosphorus insecticides, by Wet Air Oxidation (WAO) process. Experiments which commercial Pd/AC catalyst was used have been done in a batch reactor system at pH 5.5-6.0 with 500 rpm stirrer speed. In experimental studies, the effects of different pressure, temperature and amount of catalyst to the removal efficiency of carbofos were investigated. As a result of the studies, 363 K temperature, 2.0 MPa pressure and 0.03 g Pd/AC catalyst amount were found as the optimum conditions and in these optimum conditions the removal efficiency of carbofos was 85.53 %. In conclusion, it is found that Pd/AC catalyst is effective in treatment of carbofos by WAO process.