Concern is nucleation of the gamma-form in isotactic polypropylene (iPP) when applying high pressure (HP) together with a nonisothermal history. Crystallization of neat iPP (3250MR1, Arkema) and iPP with addition of 0.2 wt% of selected nucleating agents is studied. The selected nucleating agents are commercial alpha-nucleants (Hyperform HPN-20E (Milliken Chemical) and poly(tetrafluoroethylene) particles (Polysciences Inc.)), and a beta-nucleant synthesized by us (calcium pimelate). Specimens are crystallized under pressure ranging from 1.3 to 300 MPa, during cooling at approx. 8 °C/min. Specimens are then analysed by different methods to examine spherulitic structure, crystallinity, and contents of crystallographic forms. PP with HPN-20E and PTFE display the highest nucleation the gamma-form of iPP under high pressure during cooling. The increase of the gamma phase content increases the temperature of crystallization (Tc) and reduces the spherulites size. PP with calcium pimelate had no such strong effect because of the additional competitive effect of the beta-form nucleation. Keywords: Nonisothermal Crystallization, High Pressure, Nucleation, Gamma Form, Isotactic Polypropylene