The structure and properties of binary blends composed of poly(lactic acid) (PLA) and fibrous poly(butylene succinate) (PBS), which were prepared by an uniaxial stretching operation in the molten state, were studied and compared with those of blends having spherical particles of PBS in a continuous PLA phase. We found from electron microscope observation that PBS nanofibers with a large aspect ratio were generated in the stretched samples. Enlargement of the surface area of the PBS particles, which showed nucleating ability for PLA, led to a high degree of crystallization and enhanced the cold crystallization in the heating process. Moreover, the PBS fibers in the stretched samples had a dominant effect on the mechanical properties in the point range between the glass-transition temperature of PLA and the melting temperature of PBS. (C) 2010 Wiley Periodicals, Inc. J Appl Polym Sci 117: 2226-2232, 2010