During the past decade, increasing environmental awareness has renewed the interest in natural fiber reinforced thermoplastics. In current work, injection-molding method was utilized in manufacturing polypropylene (PP) composites reinforced with 20, 25, 30, and 35 wt% jute fibers. In order to increase the adhesion between the jute fiber and PP matrix, manufactured composites were post treated with maleic acid. Microstructural analysis and mechanical testing were subsequently carried out. Post treated specimens yielded better mechanical properties compared to the raw ones, while 30% fiber reinforced composites had the optimum set of mechanical properties. According to the authors, chemical modification of the PP matrix may improve mechanical properties at higher fiber content by having better interfacial bonding between the PP matrix and maleic acid post treated jute fiber.