Effluent from palm oil mill has to be treated to comply with the regulatory standards set by the Department of Environment (DOE). Even though several treatment systems have been introduced and successfuly applied, there are still some mills which fail to obtain the required quality. This paper reports an adsorption method using boiler fly ash to reduce impurities such as colour, Biological Oxygen Demand (BOD) and Total Suspended Solids (TSS)from palm oil mill effluent. Results showed that boiler fly ash was able to decolourize effluent effectively. BOD was reduced about 62% at quantity of fly ash at 200 g l^-1. Maximum reduction of TSS was at 100 g l^-1. Results also showed that pH of the filtrate increased with an increase of boiler fly ash.