A study on the crystallization and melting behaviors of blend fibers consisting of two types of polypropylene (PP), i.e. high stereo-regularity/high molecular weight PP (HPP) and low stereo-regularity/low molecular weight PP (LPP), was carried out. Blend fibers consisting of various HPP/LPP compositions were prepared through the melt spinning process. Differential scanning calorimetry (DSC) and wide-angle X-ray diffraction (WAXD) analysis were applied for clarifying the crystallization and melting behaviors of individual components. Continuous endothermic heat was detected between the melting peaks of LPP at around 40 °C and that of HPP at around 160 °C in the DSC measurement of blend fibers with high LPP composition. Such endothermic heat was more distinct for the blend fibers with higher LPP content indicating that the crystallization of LPP in the spinning process was promoted after the emerging of HPP crystals. On the other hand, heat of crystallization was detected at around 90 °C in the case of blend fibers with LPP content of 30 to 70 wt%, indicating that the crystallization of HPP component was taking place during the heating of blend fibers in the DSC measurement. These results suggested that the crystallization of HPP in the spinning process was hindered by the presence of LPP, whereas that of LPP was promoted by the presence of HPP. In the WAXD analysis during the heating of single component HPP fibers, intensity of crystalline peak was almost constant and started to decrease near the melting temperature, whereas there was a distinct increase of crystalline reflection intensities at around 170 °C, right before the melting of HPP, in case of blend fibers. This is an evidence for the occurrence of melting and re-crystallization of HPP component in the heating process.