Composite systems of Kevlar, poly(p-phenylene terephthalamide), and Santoprene, a polyolefin-based thermoplastic elastomer, were studied. Kevlar pulp was used as-received in one system, and modified in the other. The as-received Kevlar pulp was found to reinforce Santoprene to a certain degree. It was found that with increasing amount of Kevlar in the composite, low-strain modulus and tensile strength increased, while the elongation st break decreased sharply. To improve mechanical properties of the composite, hydrolysis of Kevlar pulp surface was employed in conjunction with maleic anhydride-grafted-polypropylene (MA-g-PP), a reactive compatibiliser. It was found that the treated Kevlar pulp greatly improved the low-strain modulus, tensile strength, and elongation at break of the composite. Dynamic mechanical analysis showed that the storage modulus of the Kevlar/MA-g-PP/Santoprene composite was significantly higher than the as-received Kevlar composite. A slight increase in transition temperatures of polypropylene matrix was also observed. As a result of the fact that low-strain modulus and tensile strength of the composite were improved when hydrolysed Kevlar pulp and MA-g-PP were used, it is suggested that such a combination might have increased the interfacial adhesion of the fibre and the matrix, and effective fibre volume fraction, resulting in a better distribution of stress along the reinforcing fibre.