This work presents a new empirical method to analyse the non-isothermal crystallization kinetics of polypropylene. The Kissinger analysis, widely used in the literature to calculate an activation energy of the crystallization mechanism, was critically examined regarding its applicability to the crystallization process of semicrystalline polymers. The analogy between the systems modelled by Kissinger and polymer crystallization applies only in very restrictive cases, and the activation energy, as commonly used, is an ill-defined quantity. Nevertheless, it was shown that the Kissinger analysis yields a phenomenological parameter, here called REact, related to the crystallization kinetics at moderately high cooling rates (up to ~50 °C s−1). This parameter, created with data obtained on more than 20 poly(propylene) compounds based on four different base polymers of different chain structure and composition, correctly estimates the crystallization performance of different systems at higher cooling rates, demonstrated by a good correlation between REact and the morphology formed in cable extrusion and cast film extrusion processes.