A dual-band cavity-backed circularly polarized crossed-dipole antenna with double split-ring resonators (SRRs) is investigated in this paper. A pair of crossed dipoles connected by concentric ring-delay lines is firstly designed as a circularly polarized (CP) antenna with only one CP mode. To extend the operation of the original design, a pair of the λ/4-resonance SRRs are used to realize wider axial ratio bandwidth at higher band. At the same time, another pair of the λ/4-resonance SRRs with larger dimension is adopted to obtain a lower frequency band, although the effect is not very satisfying. Then the cavity-backed technology and a defected ground structure are both employed to improve the working bandwidth. The dual-band CP antenna can be tuned into a wide bandwidth one by changing the dimensions of the larger SRRs. A good agreement between the simulated and measured results can be observed. The measured impedance bandwidths are 6.90% (3.36-3.60 GHz) and 53.58% (4.40-7.62 GHz). The measured 3-dB AR bandwidth is 7.93% (3.39-3.67 GHz) and 59.15% (4.08-7.51 GHz).