Abstract: A novel multi-resonant element is proposed for dual-band frequency selective surface (FSS) designs where close band spacing is required. The element is constructed by interlacing four I-shaped patches and is called interlaced I-shape (IIS) element. The lowest two resonant frequencies of an IIS based FSS can be adjusted independently by tuning one or two of its geometry parameters. Compared with other known FSS elements, the IIS-FSS is compact and is able to achieve very close band spacing without requiring extremely small clearance. The frequency responses of the IIS-FSS are verified through both simulations and experiments.