Currently the most viable way toward ecofriendly composites, with a less expensive price, is the use of natural fibers as reinforcement. This situation makes necessary the use of low cost fillers as a way of reducing the cost of the end product. The partial or total substitution of PHBV by lignocellulosic fiber could be of interest. PHBV can be reinforced with natural fiber in order to enhance its mechanical properties and to reduce the cost of final product. Although, there are a few hydroxyl and carboxylic groups on ends of PHBV molecular chain some degree of possible dipolar interactions among moderately polar (C=O) and polar groups (–OH and –COOH) of PHBV and hydroxyl group (–OH) of cellulosic fiber can provide an opportunity for an interfacial interaction between the fiber and the matrix. In this study, alfa fiber and its cellulose obtained after extraction were used as reinforcement for the development of totally biocomposite materials. This work characterization of tensile properties and a comparison between alfa fiber and its cellulose effect on poly (hydroxybutyrate-co-valerate) (PHBV) composites. Owing to higher production cost of PHBV as compared to traditional polymers, we investigated the possibility to replace a quantity of PHBV by lignocellulosic filler without damaging the properties of the polymers. The results show a narrow increasing trend in the tensile strength; this could be attributed to the compatibility between the filler and PHBV. [2] The tensile modulus of PHBV based composite was increased compared to neat PHBV. The diffraction profile of PHBV matrix is very similar of that presented for composites. Both PHBV, PHBV/alfa fiber and PHBV/cellulose shows reflections at the same values as for the neat biopolymer, indicating that addition of reinforcement does not alter the unit cell after incorporation of alfa fiber and its cellulose. Keywords: Cellulose,biopolymer, biocomposites, thermal properties.