The crystallization of isotactic polypropylene (iPP) in the presence of its own fiber or/and alpha nucleating agents, i.e., DBS and NA11, was studied. The results show that both nucleating agents exhibit nucleation ability toward iPP and accelerate iPP melt crystallization. This is manifested by an upward shift of crystallization temperature by up to 10 degrees C compared with its bulk crystallization. The iPP fiber exhibits also high nucleation ability toward the iPP matrix as demonstrated by the formation of transcrystalline layers. The crystallization of iPP in the nucleated iPP matrix/fiber system shows that the nucleating agents do not affect the transcrystallization of iPP surrounding its fiber. This indicates that the fiber exhibits higher nucleation ability toward iPP than the nucleating agents. On the basis of the exact same chemical and crystallographic structures of the iPP fiber and matrix, the results demonstrate the importance of structure similarity and matching between the crystallographic structures in the heterogeneous nucleation of polymers.