Recently, researchers are focused on the use of biomasses generated in oil palm industry as compost to overcome their negative impacts and recycle them to produce a useful byproduct for agriculture. This study investigated formation of compost from Palm Oil Biomass (POB) by adding Cow Dung (CD). The experiment was carried out under shade in plastic bins at different POB and CD ratios (4:0, 3:1, 1:1 and 1:3) to activate decomposition mechanism up to 11 weeks. Decomposing materials was frequently moistened and turned accordingly. The addition of CD has facilitated the co posting process and treatment with 1:3 ratio of POB and CD had better quality than other treatments such that the C/N ratio, the Electrical Conductivity (EC) and pH for mature compost were 22.2, 2.83 mS.m-T and 7.81 respectively. © 2015, Korean Society of Civil Engineers and Springer-Verlag Berlin Heidelberg.