To improve the structure and hard elasticity of poly(vinylidene fluoride) (PVDF) fibers, a small amount of the plasticizer dibutyl phthalate (DBP) was added to PVDF. The PVDF/DBP blend fibers were prepared by melt spinning and subsequent annealing. The crystalline structure and thermal properties of the blend fibers were analyzed in terms of the long-period lamellar spacing, crystal structure, and degree of crystallinity with X-ray diffraction, differential scanning calorimetry, and small-angle X-ray scattering. The results indicated that stacked crystalline lamellae, which were aligned normal to the fiber axis, existed in the blend fibers, and they were in the form of an alpha-crystal phase. The total crystallinity of the blend fibers was higher than that of the pure PVDF fibers, and it reached its highest value when the DBP concentration was 2 wt %; then, it decreased with an increase in the DBP content. The morphology and mechanical properties of the fibers were also investigated with scanning electron microscopy and electronic tensile experimentation. The results of scanning electron microscopy apparently exhibited a small porous structure on the surface of the blend fibers, and the more DBP there was in the PVDF fibers, the more porous structure was obtained. Mechanical experiments indicated that the fibers with a 5 wt % concentration of DBP had better elastic recovery and breaking strain than the pure PVDF fibers. These results all indicated that DBP-modified PVDF fibers have potential applications in preparing microporous membranes by a melt spinning and stretching process. (C) 2009 Wiley Periodicals, Inc. J Appl Polym Sci 114: 3645-3651, 2009