In Malaysia, there are presently 4.3 million hectares of oil palm plantation, which produce over 100 million tonnes of biomass, such as empty fruit bunches (EFB), kernel shells (oil palm shell or OPS) and pressed fruit fibres (PPF) from mills, as well as oil palm fronds (OPF) and oil palm trunks (OPT) from fields. In this work, proximate, ultimate, hydrolysis and heating value analyses were carried out on EFB, OPS and OPF. The results demonstrated that dried unwashed EFB, OPS and OPF have a moisture content of 7.01 mf wt%, 3.44 mf wt% and 8.01 mf wt%, respectively, with high volatile matter of approximately 75–82 mf wt% and ash content of approximately 4 mf wt%. The higher heating values (HHV) of the samples were determined using a bomb calorimeter technique. A simple water washing pre-treatment was also employed to study ash reduction in EFB, OPS and OPF. A high char yield was obtained by slow pyrolysis while minimising liquid and gas yields. It was determined that the carbon content was high for samples with low ash content. Furthermore, the washed and unwashed samples were analysed by thermogravimetric analysis to determine their thermal degradation behaviour.