The potential of wheat straw fibers prepared by mechanical and chemical processes as reinforcing additives for thermoplastics was investigated. Fibers prepared by mechanical and chemical processes were characterized with respect to their chemical composition, morphology, and physical, mechanical and thermal properties. Composites of polypropylene filled with 30% wheat straw fibers were prepared and their mechanical properties were also evaluated. The fibers prepared by chemical process exhibited better mechanical, physical and thermal properties. Wheat straw fiber reinforced polypropylene composites exhibited significantly enhanced properties compared to virgin polypropylene. However, the strength properties of the composites were less for chemically prepared fiber filled composites. This was due to the poor dispersion of the fibers under the processing conditions used. These results indicate that wheat straw fibers can be used as potential reinforcing materials for making thermoplastic composites.