In this communication, a novel triple band frequency selective surface (FSS) designed for Global System for Mobile Communications (GSMs) frequency bands is presented. Unit cell of the proposed FSS consists of one rectangular-shaped resonator designed for 942 MHz and one synthetic resonator designed for both of 1842 and 2142 MHz frequencies. A novel technique is introduced to design a synthetic resonator in which two loop-shaped resonators intersect to each other resulting a unique resonator operating at two frequencies. The proposed design has the advantages of separating two very closely spaced frequency bands as in GSM systems with a narrow notch between the two frequencies of 1842 and 2142 MHz. Furthermore, a very low-frequency response sensitivity to the oblique incidence angles is achieved by using a miniaturized single synthetic resonator for the two frequencies in a single layer. Good agreement is observed between the measured and simulated results. A minimum of 20-dB attenuation for the transmission coefficient is achieved in all downlink frequency ranges of GSM system with a good stability against the oblique angle of incidence for both transverse-electric and transverse-magnetic polarizations.