All polymer composites contain blends of two or three polymers of which the minor phase is in fibrous form and acts as the reinforcement for the material. In the present studies polypropylene (PP) with nylon (Ny) were compounded extruded and then molded at temperature close to nylon. Crystallization kinetics and structure devlopment was studied in the PP-Ny blends with composition. Nylon dispersed phase was found to nucleate PP giving rapid crystallization. There was extensive fibrous morphology and fiber diameter was dependent on composition. The tensile and impact strength were considerably improved by almost 1.5 to 2 times that of PP at certain concentrations of nylon. Thus, these blends behave as self reinforced composites due to the peculiar nanofibrous morphology getting developed during melt processing.