A dual-band circularly polarized (CP) electromagnatic band-gap (EBG) resonator antenna (ERA) is presented. The antenna employs an all-dielectric superstructure, which consists of two identical unprinted dielectric slabs, and a dual-band corner-truncated patch feed. A prototype antenna is fabricated and tested using a superstructure made out of 3.175-mm-thick Rogers TMM10 material. Measured peak gains are 16.1 dBic [left-hand circular polarization (LHCP)] and 16.2 dBic [right-hand circular polarization (RHCP)], measured radiation efficiencies are 93% and 91%, and the boresight axial ratios are 1.9 and 1.5 dB at 9.65 and 11.75 GHz, respectively. This dual-band antenna is easy to fabricate, making it suitable for high-gain low-cost CP applications.