Fracture behavior of polypropylene (PP)/ethylene-propylene-rubber (EPR) blends containing small crystal in elastomeric phase was investigated. Various ethylene-alpha-olefin copolymers (ECP) were used as crystal components and put into the elastomer phase of the blends. The crystallite size was controlled by changing the composition of the ECP. From thermal analysis and electron microscopic analysis, it was found that the ECP having a smaller crystal had better affinity to EPR and thus the crystal was finely dispersed in the elastomeric phase. The ECP with large crystallite size had poorer affinity to EPR and tended to segregate in the elastomeric phase. Scratch resistance and tensile elongation of blends were measured and it was found that the small crystal drastically improved the above properties while the large crystal deteriorated them. The dispersed small crystal was thought to act as a crosslinking point in the elastomeric phase. The reinforcement of the elastomeric phase by such quasi-crosslinking structure was the possible reason for the improvement of the mechanical properties of the blends.