Isotactic polypropylene (iPP) is a semi-crystalline polymorphic thermoplastic. The nucleation growth and the formation of semi-crystalline superstructures like spherulites during processing depends on temperature, pressure and time. In this study, the thermal crystallization kinetics of iPP grades with different melt flow rates (MFR) were investigated. Using dynamic differential scanning calorimetry (DSC) and heating stage experiments under the polarized light microscope (POM), the melting and crystallization behavior of the materials was analyzed. Furthermore, the molecular weight and molar mass distribution of the materials were determined using gel permeation chromatography (GPC) and conclusions were drawn about the influence on the crystallization behavior, taking into account the previous thermal analysis. The aim is to gain a better understanding of the crystallization behavior of iPP, which is required for the modeling of crystallization processes and thus for the prediction of process-induced morphological properties of products made from iPP. The work of Yvonne Spoerer forms part of the DPI program, project #816t18.