The influence of different conditions on the mechanical properties of short coir fiber reinforced polymer composites as well as glass fiber reinforced polymer composites have been analyzed and compared. Fiber length of 20 mm was found to be optimum for the best result. It is observed that the filler loading of 30 phr was most suitable for best results. Degradation studies were carried out in different solvents like 10% NaOH, 1 N HCl, and 10% NaCl and water. The effect of these solvents and water on the mechanical properties of the composites was studied in detail. The deterioration of mechanical properties of the coir/PE and glass/PE composites by environmental weathering was also studied.