In this paper, we describe a new design for a magnetic planetary gearbox. We discuss the theory of operation and a simulated design. We constructed and verified the simulation by measuring the transmitted torque and cogging torque. A magnetic planetary gearbox operates like a mechanical planetary gearbox, except that it is contact-free and needs no gear lubrication. Hence, it has the same characteristics of three transmission modes, a high-speed-reduction ratio, and high durability. The starting point for the design procedure is to avoid possible sliding (i.e., pole-slipping), and we propose three steps to obtain the maximum number of magnetic planet gears. We show that using more planetary gears is a way to increase the transmission torque. Cogging torque can be high in this design. We assessed this potential by using finite-element analysis and then measuring performance of the fabricated gearbox. While the simulation overestimates the cogging torque (for various reasons), we propose a method to reduce the cogging torque to a very low value. We present a literature review to illustrate the development of magnetic gearing and highlight the innovation of this design.