In view of to higher production cost of polyhydroxybutyrate-covalerate (PHBV) as compared to traditional polymers, we opt at the possibility to replace a quantity of PHBV by lignocellulosic fiber without damaging the properties of the composites. This study highlights the effect of fiber loading and pretreatment on properties of biocomposites based on PHBV. Thus, the biocomposites containing 10, 20 and 30 wt.% of olive husk flower (OHF) with and without pretreatment were prepared by using a co-rotation twin screw extruder followed by injection molding. Tensile modulus of biocomposites increased with fiber loading and with pretreatment but tensile strength decreased, whereas, the pretreatment of OHF enhances this property due to the better interfacial interaction of the PHBV biopolymer and the reinforcement after pretreatment. This result was confirmed by SEM analysis. Indeed, the surface of composites prepared with OHF pretreated had less voids and cavities suggesting a good adhesion between the two. Thermogravimetry analysis showed also that composites with pretreatment have enhanced thermal properties when compared with the composites without pretreatment.