With the rapid development of detection technologies, compatible stealth in the infrared and radar ranges has become increasingly essential not only for military application but also for personal privacy protection. In this study, we design a metamaterial window that possesses stealth ability in both the thermal infrared and broadband microwave ranges, using a particle swarm optimization algorithm to realize multi-band optimization. We experimentally verify that the proposed structure can achieve over 90% microwave absorption in the range 5.1 to 19.2 GHz (covering the X and Ku bands), with low infrared emissivity (∼0.15), and also maintain visible transmittance above 60%. Moreover, the window retains good performance up to 200 °C owing to the intrinsic properties of the material. Our multi-band optimization method enables the application of the transparent metamaterial windows in electromagnetic shielding and stealth and can potentially be applied in smart window related industries.