The effect of polyvinylidene fluoride (PVDF) on the crystallization behavior of polyoxymethylene (POM) was investigated using polarized light microscopy, wide angle X-ray diffraction, and differential scanning calorimetry. From these results, it is seen that with the addition of PVDF, the spherulitic size of POM was greatly decreased, but no change occurred for the hexagonal system of POM crystal. Three methods, namely, Avrami, Ozawa, and Mo, were carried out to analyze the nonisothermal crystallization data. The results showed that the PVDF dispersed in POM acted as the heterogenous nuclei and accelerated the rate of nucleation, but hindered the crystal growth rate of POM which can be seen from the activation energy of pure POM and POM/PVDF blend. POLYM. ENG. SCI., 47:2034-2040, 2007. (C) 2007 Society of Plastics Engineers.