This research investigated the effect of steam treatment on the properties of particleboard panels manufactured from oil palm trunk with addition of polyhydroxyalkanoates (PHA) at different percentages. Particles were treated by steam at a temperature of 130°C for 30min. The mechanical and physical properties of the experimental panels including modulus of rupture (MOR), internal bond strength (IB), thickness swelling (TS), water absorption (WA) and surface quality were investigated. Further analyses of the specimens were also conducted using gas chromatography, thermogravimetric analyzer, Fourier transform infrared spectroscopy, X-ray diffraction and field emission scanning electron microscopy. Addition of PHA to oil palm particles enhanced MOR and IB as well as dimensional stability of the panels. The highest MOR and IB values of 8.76MPa and 1.02MPa were determined for the panels made with 10% pure PHA, respectively. It appeared that all properties of the specimens minimally increased with increasing PHA content in the panels. Based on the results of this work PHA could be considered as a potential additive to improve overall properties of such composite panels from oil palm which is an important agricultural crop in Malaysia.