Bacillus subtilis was immobilized in polyurethane foam (PUF) and subsequently the biofilm was allowed to grow up to twelve days. The developments of microorganisms on the PUF surface were observed in different day’s intervals. The optical microscopic observations clearly discriminated the formations of biofilm on the PUF. Afterwards, batch experiments were carried out to study the degradation of pulp and paper mill effluent by using immobilized polyurethane foam (IPUF) under three different circumstances; with and without nutrients to the IPUF and PUF alone i.e., without microorganisms and nutrients. The experimental results revealed that the IPUF with nutrients had effectively reduced the effluent color, biochemical oxygen demand and chemical oxygen demand within the five days of treatment.