Submerged and confined multiple jet impingement is widely implemented in cooling applications since it provides high heat transfer coefficients and heat transfer uniformity. Its performance depends on several variables that make it complex and difficult to control. To understand the physical phenomena and characterize the flow field, an in-depth study using Particle Image Velocimetry (PIV) technique and heat transfer sensors is conducted in this study. The PIV measurements provide relevant data, but their accuracy depends on an effective experimental setup and a careful selection of the most appropriate tracer particles. Therefore, this work presents the experimental apparatus and comprises an analysis of the efficiency of different seeding particles. The results demonstrate the complexity of the jet flow impinging on a step surface, which induces a strong flow reversal that affects the jet flow development and the interaction with the adjacent jets. The large-scale structures induced in the vicinity of the target plate are captured by the PIV, as well as the strong fountain flows generated between the adjacent jets. This increased turbulence leads to an increase in heat transfer which is measured by the heat flux sensors, corresponding to a Nusselt number 25% greater for the case of a 2 D step plate. Through this study, relevant insights for several engineering applications that use multiple jet impingement are provided, highlighting that the combination of PIV and heat flux sensors is appropriate to characterize the jet’s flow dynamics and the heat transfer of this complex process.