Natural fiber is incompatible with hydrophobic polymer due to its hydrophilic nature. Therefore, surface modification of fiber is needed to impart compatibility. In this work,superheated steam (SHS)-alkali was introduced as novel surface treatment method to modify oil palm mesocarp fiber (OPMF) for fabrication of biocomposites. The OPMF was first pre-treated with SHS and subsequently treated with varying NaOH concentration (1, 2, 3, 4 and 5%) and soaking time (1, 2, 3 and 4h) at room temperature. The biocomposites were then fabricated by melt blending of 70 wt% SHS-alkali treated-OPMFs and 30 wt% poly(butylene succinate) in a Brabender internal mixer followed by hot-pressed moulding. The combination treatment resulted in fiber with rough surface as well as led to the exposure ofmicrofibers. The tensile test result showed that fiber treated at 2% NaOH solution and 3h soaking time produced biocomposite with highest improvement in tensile strength (69%) and elongation at break (36%) in comparison to that of untreated OPMF. The scanning electron micrographs of tensile fracture surfaces of biocomposite provide evident for improved adhesion between fiber and polymer after thetreatments.This work demonstrated that combination treatments of SHS and NaOH could be a promising way to modify OPMF for fabrication of biocomposite.