A passive lossless snubber circuit for multilevel inverters is proposed in this paper. The topology is simple and requires no extra control circuit. In order to reduce the high-voltage stress on power switches with this snubber circuit, an improved snubber circuit is presented by adding separate low-power direct current voltage sources into the original one. The operating principles and design considerations are described in detail in this paper. A prototype of a three-phase three-level diode-clamped inverter with the improved passive lossless snubber is built and tested. The simulation and experimental results indicate that not only can it realize the soft switching operation of the three-level inverter with low-voltage stress but also the topology and the control are simple.