The aim of this study is to investigate the effectiveness of Isora fiber mixed with 1% ricinoleic acid as a reinforcement for polypropylene (PP) thermoplastic matrix. Isora fibers were subjected to mercerization prior to blending with PP in order to obtain good interfacial adhesion with the matrix. A PP/Isora composite has been prepared by melt blending of PP with 5%, 10%, 15%, 20% alkali treated Isora fiber in co-rotating twin screw extruder. The extruded strands are pelletized and then injection-moulded to obtain specimens. The optimum compositions of the PP/alkali treated Isora composites were mixed with 1% ricinoleic acid. Fiber-matrix adhesion will be analysed by mechanical and thermal properties of the composites which were evaluated.