A broadband circularly polarized (CP) omnidirectional antenna employing circular open-loops is investigated. The proposed antenna consists of four circular open-loop elements that have been printed around a hollow cylinder, each element has a main open-loop and a parasitic open-loop, a broadband feed network is used to excite four main open-loops, a metal reflection column is introduced in the center of cylinder for improving CP performance. It is shown that the broadband circularly polarized omnidirectional antenna achieves a bandwidth of ∼30% (1.67–2.25 GHz) with return loss > 10 dB, and ∼32% (1.67–2.31 GHz) with axial ratio (AR) < 3 dB. The gain is stable with the variation of less than 1 dB.