AbstractThis article presents the design of a novel miniaturized 2.5D frequency selective surface (FSS) for radiofrequency and microwave shielding applications is proposed. The proposed FSS is configured to offer multiple band‐stop characteristics with a wide frequency ratio. The unit cell is developed using traces that run on the top and bottom layers of the substrate with traces connected using vias. This proposed unit cell structure provides distinct operating modes at high and low frequencies. The proposed FSS unit cell has a compact geometry with a foot‐print of 0.059λo × 0.059λo where λo is the freespace wavelength. The FSS unit cell is polarization insensitive and exhibits good angular stability up to 45°. A prototype FSS is fabricated to validate the simulation results. The miniaturized FSS can be used as a shield at terrestrial frequencies and satellite frequencies making it usable for both indoor and outdoor environments.