The design of a rim-driven pumpjet thruster (RDPJ) is addressed through a simulation-based design optimization approach. The working framework consists of a parametric description of the rim blade, duct and stator blades geometries and a multi-objective optimization algorithm which makes use of the results from high-fidelity RANS calculations to drive the choice towards optimal shapes. In two distinct design runs, both the rotor/stator (RDPJ-R/S) and the stator/rotor (RDPJ-S/R) configurations are considered for the optimal design from a multi-objective optimization process. The design aims to balance two opposing goals: maximizing propulsive efficiency and minimizing cavitation, the latter assessed using a simple inception criterion derived from the analysis of non-cavitating pressure distribution across the blade surface. A constraint on the delivered thrust fixes the functioning condition of the devised thrusters. The optimal geometries in both RDPJ-R/S ans RDPJ-S/R configurations are extracted as main outcome of the work while design trends and guidelines are extracted from the analysis of the amount of data collected during the optimization process.