The main aim of the proposed research is to study properties of Polyhydroxybutyrateco-valerarate (PHBV) based green composites reinforced with lignin based carbon fibres. In order to understand the mechanism of carbon fibre-matrix interaction and process engineering during composite fabrication, commercial carbon fibre were used in this piece of investigation to extend the developed research on to lignin based carbon fibres. The advanced biocomposites from carbon fibre and PHBV bioplastic were prepared with extrusion compounding and injection molding techniques. The effects of fiber length and fiber loading, on the performance of PHBV/carbon fibre composites were studied. The mechanical properties such as tensile and flexural strength/modulus of the composites significantly increased with the fibre length as well as fibre loading. The thermomechanical behavior such as heat deflection temperature (HDT) and storage modulus of the composites were determined by dynamic mechanical analysis (DMA). HDT values of the composite materials increased with the carbon fibre loading and fibre length. The DMA results reveal that the storage modulus of PHBV/carbon fibre composites was higher when compared to the matrix. Scanning electron microscopy (SEM) was used to observe the adhesion between fibre and matrix. The tensile modulus of the composites were evaluated theoretically by Hirsch model.