Isotactic polypropylene (iPP) is a widely used commodity plastic due to its good combination of good mechanical properties and low price. To even further expand the possible applications of this material, an interest in toughening iPP has been increasing over the past years. iPP is a polymorphic material and can crystallize in different modifications where the thermodynamically metastable beta modification exhibits a higher toughness than alpha modification that is usually found under normal processing conditions. The easiest and industrial most relevant method to obtain a high amount of beta phase is the use of nucleating agents. Many studies have investigated the influence of different nucleating agents in iPP over the past years. However, only little information is available about difficult-to-toughen iPP grades with high melt flow rates even though these are very relevant for injection molding applications. The influence of two different 1,3,5-benzenetrisamide-based experimental beta-nucleating agents on the morphological and mechanical behavior of isotactic polypropylene with a melt flow rate of 120 g/10 min is investigated and compared to a commercial bisamide-based beta-nucleating agent and a 1,3,5-benzenetrisamide-based alpha nucleating agent. Morphological investigations by wide-angle X-ray scattering (WAXS) show that only 0.04 wt. % of one of the experimental additives is enough to induce high amounts of beta modification in the crystalline part of the polymer. The materials are investigated with quasistatic (tensile testing) as well as short-time dynamic (Charpy impact strength) methods. A much higher toughness of the material containing the experimental beta-nucleating agents can be observed. This behavior is correlated with the different influences of the different additives on the morphology of iPP.