A frequency selective surface (FSS), whose unit cell consists of a ternary tree loop loaded with a modified tripole, is proposed to block multiple frequency bands. Target frequency bands correspond to Korean personal communication services, cellular mobile communication, and 2.4 GHz industrial, scientific, and medical bands. Through the adjustment of inter-element and inter-unit cell gaps, and adjustment of the length of elements, we present an FSS design method that makes the precise tuning of multiple resonance frequencies possible. Additionally, to verify the validity of our approach, simulation results obtained from a commercial software tool and experimental data are also presented. knowledge, an FSS with a unit cell made up of those two elements together has not been treated carefully. Therefore, we propose a ternary tree loop combined with a tripole as our unit cell geometry. Additionally, we present a successfully frequency-tuned response of our FSS by considering the effect of the equivalent capacitance between unit cell elements. To confirm the validity of our approach, experimental data are presented with the simulation results achieved by CST Microwave Studio (MWS) and Ansoft HFSS.