Liquid-liquid (GL) phase separation and its effects on crystallization in polypropylene (PP)/ethylene-propylene rubber (EPR) blends obtained by melt extrusion were investigated by time-resolved light scattering (TRLS) and optical microscopy. GL phase separation via spinodal decomposition (SD) was confirmed by TRLS data. After L-L phase separation at 250 degreesC for various durations, blend samples were subjected to a temperature drop to 130 degreesC for isothermal crystallization, and the effects of GL phase separation on crystallization were investigated. Memory of the GL phase separation via SD remained for crystallization. The crystallization rate decreased with increasing GL phase-separated time at 250 degreesC. Slow crystallization for the long GL phase-separated time could be ascribed to decreasing chain mobility of PP with a decrease in the EPR component in the PP-rich region. The propylene-rich EPR exhibited good affinity with PP, leading to a slow growth of a concentration fluctuation during annealing,