Agro-based renewable materials have received significant attention in recent years because of their low cost, light weight, ecofriendliness, and worldwide environmental awareness. In the present work, coir fiber reinforced polypropylene composites were manufactured using injection molding method. Raw coir was chemically treated with benzene diazonium salt in alkali, acidic, and neutral media separately in order to increase the compatibility between the coir fiber and polypropylene composite. During chemical treatment, hydrophilic -OH groups in the raw coir cellulose were converted to hydrophobic -O-Na groups. Both raw and treated coir at 10, 15, 20, 25, 30, and 35 wt % were utilized during composite manufacturing. Microstructural analysis and mechanical tests were conducted. Alkali treated specimens yielded the best set of mechanical properties. On the basis of fiber loading, 30% fiber reinforced composites had the optimum set of mechanical properties among all composites manufactured.