Abstract The objective of this work is to evaluate the mechanical properties and durability performance of bio-composite materials made from sawdust and thermoplastic polymer (HDPE). For the preparation of the composites, sawdust in different proportions with Maleic Anhydride grafted Polyethylene (MAPE) as coupling agent was used. The mechanical properties in addition to water absorption were successively characterized. Scanning electron microscopy (SEM) was used to analyze morphological structure alteration when exposed to intense weathering. For mechanical properties tensile test was performed at room temperature while for water absorption samples were immersed in water for more than ten weeks. In addition, the biodegradability of bio-composites up to fourth months was investigated and the results indicated that by increase of filler content the amount of weight loss increased as well. In other words, even though addition of sawdust to thermoplastic polymer improves mechanical performance of composite material, it also accelerates the biodegradation rate of the composite. An optimum amount of fillers content might compromise the effect of biodegradation and mechanical properties of composite materials. Keywords: Biodegradability, Mechanical properties, Thermo-physical properties, Morphological structure.