The non-isothermal crystallization (NIC) of isotactic polypropylene (iPP) and its composites with submicronic talc particles (μ-talc) was investigated by differential scanning calorimetry. The modeling of the NIC kinetics of the iPP matrix was performed using Jeziorny-modified Avrami’s model, Ozawa’s and Mo’s theoretical approaches. The Jeziorny’s and Ozawa’s theories allowed us to confirm that the μ-talc filler particles significantly promote the NIC kinetics of the iPP matrix which noticeably manifests itself via a change in the nucleation mechanism. However, Mo’s model proved to be the more relevant model to account for the NIC of the present materials. In parallel, the activation energy and nucleation activity of NIC were calculated by Kissinger’s and Dobreva’s methods, respectively. Both approaches reveal that a maximum nucleation activity of μ-talc takes place for 20% filler content. This finding is discussed in relation to the μ-talc content thresholds of mechanical percolation and crystallinity saturation that were reported in previous studies for these composites, about 10 and 30% μ-talc, respectively. An endeavor of physical explanation for these phenomena is put forward. © 2019, Akadémiai Kiadó, Budapest, Hungary.