Increasing turbine inlet temperature is one of the main strategies used to accomplish the demand for increased performance of modern gas turbines. Thus, optimization of the cooling system is becoming of paramount importance in gas turbine development. Leading edge (LE) represents a critical part of cooled nozzles and blades, given the presence of the hot gases stagnation point, and the unfavorable geometrical characteristics for cooling purposes. This paper reports the results of a numerical investigation, carried out to support a parallel experimental campaign, aimed at assessing the rotation effects on the internal heat transfer coefficient (HTC) distribution in a realistic LE cooling system of a high pressure blade. Experiments were performed in static and rotating conditions replicating a typical range of jet Reynolds number (10,000–40,000) and Rotation number (0–0.05). The experimental results consist of flowfield measurements on several internal planes and HTC distributions on the LE internal surface. Hybrid RANS–large eddy simulation (LES) models were exploited for the simulations, such as scale adaptive simulation and detached eddy simulation, given their ability to resolve the complex flowfield associated with jet impingement. Numerical flowfield results are reported in terms of both jet velocity profiles and 2D vector plots on two internal planes, while the HTC distributions are presented as detailed 2D maps together with averaged Nusselt number profiles. A fairly good agreement with experiments is observed, which represents a validation of the adopted modeling strategy, allowing an in-depth interpretation of the experimental results.