This work presents an experimental analysis of gas–liquid flows in a centrifugal rotor prototype. Pressure rise curves are evaluated considering a wide range of liquid and gas flowrates and different rotating speeds. An innovative apparatus including a dynamic sealing system, back illumination, and filming in a rotating frame of reference is employed to visualize gas–liquid flow patterns at different operating conditions. Volume fraction measurement and bubble-size evaluation are also taken into account. The experimental apparatus allowed analyzing details of the gas-phase dynamics inside the rotor channels. That includes preferential bubble paths and zones of agglomeration, gas pocket formation, coalescence and breakup, and the effect of flow pattern transition on different degrees of performance degradation that centrifugal rotors are subject to when working with gas–liquid flows. Also, important information about the effect of the gas flowrate and the rotating speed on the performance of the assumed rotor prototype could be gathered. Discussions in this work should contribute to comprehend the behavior of gas–liquid flow in centrifugal pumps, a topic that is still far from being well understood. Qualitative and quantitative data here presented could also be valuable to guide the development of numerical models to solve this problem.