Abstract: Background and Objective: The jute fibre based composite materials have remarkable advantages of economic and environmental aspects such as low cost, low density, high strength to weight ratio and environmentally friendly. The study was focused on the composites that were prepared using unsaturated polyester as matrix and jute fibre as reinforcement by hand lay-up technique with the aim of the investigating the tensile, bending, thermal properties and water absorbency. Materials and Methods: Before fabrication of composites, jute fibres were treated with alkali and bleaching agent commonly known as combined scouring and bleaching. Composite of similar fashion was also prepared using untreated jute fibres. The composites were synthesized at 20:80 fibre-matrix weight percentages. The effect of chemical treatment was examined. The fractured surface morphology of the composites was investigated by Scanning Electron Microscopy (SEM) to comprehend the fibre-matrix interaction. The tensile, bending, thermal properties and water absorbency were studied and the results were graphically showed and explained. Results: The treated fibre composites showed higher tensile and bending strength than the untreated one. Both elastic modulus and bending modulus were also found to be higher for treated fibre composites. The treated fibres composites also exhibited lower thermal conductivity and higher thermal resistance. The untreated fibre composites become absorbent and significantly higher water absorption up to 300% and 200% than treated one in both 2 and 24 h water absorbency test. Conclusion:The behaviour of treated and untreated composites was explained by removing lignin and impurities from jute fibre that enhanced the better interaction between fibre and matrix. As natural fibres have very little resistance towards the environment, the manufactured composites can be the expedient application of biodegradable composites with auspicious physical properties. Furthermore, due to the simple manufacturing process, quicker processing time and lower manufacturing cost, the composites would be versatile material in the field of engineering and technology.