The present work deals with the utilization of oil palm mesocarp fibre (OPMF) and poly(butylene succinate) (PBS) to produce cost-effective biodegradable materials. The biocomposite was prepared from OPMF and PBS at a weight ratio of 70:30 via a melt blending technique without addition of any additive. This biocomposite showed relatively low tensile and water resistance properties. As a consequence, it was subjected to electron beam irradiation (EBI) treatment under various irradiation dosages ranging from 5-25 kGy, aiming at improving both its tensile properties and its water resistance. The results indicated that the biocomposite irradiated with 25 kGy of applied dosage showed a considerable improvement of 50% in tensile strength, 780% in tensile modulus and 38% in elongation at break. The water absorption and thickness swelling of the biocomposites were reduced after EBI treatment. The scanning electron microscopy showed improvement of the interfacial adhesion between OPMF and PBS after EBI treatment.