The influence of small amounts of poly(styrene-co-acrylonitrile) (SAN) on the non-isothermal cold crystallization behavior and morphology of poly(ethylene terephthatate) (PET) was investigated by dynamic-mechanical thermal analysis, differential scanning calorimetry (DSC), optical microscopy, and scanning electron microscopy. The results indicated that SAN had a limited solubility in the amorphous phase of PET although in a larger scale a phase separation occurred. The addition of 1 wt % of SAN promoted a significant reduction in the crystallization rate of PET, acting as an antinucleating agent. The kinetics parameters were determined applying both the Ozawa and Mo approaches. Mo's model described the crystallization evolution better than the Ozawa one because it is possible to analyze the kinetic parameters in similar range of crystallinity degrees. (C) 2009 Wiley Periodicals, Inc. J Appl Polym Sci 116: 1077-1087, 2010