This paper focuses on a topology optimization method for laminated busbars in power converters that minimizes the quantity of copper used while keeping the temperature under the allowed limits. Busbars are widely studied for adding their stray inductance to the commutation loop, which causes surge voltage across the power devices. However, the study of heat dissipation is essential to control hotspots in the busbar and preserve the converter components. Current density and temperature are sensitive to shape modifications; hence, topology optimization based on multiphysics simulations is an aspect to be considered when designing prototypes for a good cost performance ratio. The temperature is calculated by an electrothermal two-dimensional (2-D) finite element method (FEM) superposition approach. Busbar plates are modeled in 2-D since the thickness is constant. Furthermore, the different layers are related by the thermal equations reproducing the heat transfers regarding the overlap in the laminated busbar. Simulation results are validated by experimental tests. Comparison with 3-D FEM proves the 2-D approach to be faster while remaining accurate and a perfect method for topology optimization resolutions, which are very time consuming for three-dimensional (3-D) geometries. The busbar topology optimization is made by maximizing the energy transfer with the environment and by varying the electric and thermal conductivities of the mesh elements. Optimization leads to more than 50% volume reduction.