This letter presents a high-gain hybrid resonant antenna for millimeter wave (mmW) radar application. This presented antenna contains several units, each unit contains an EH₁-mode segment and a TEM-mode segment. The EH₁-mode segments are radiative, and the TEM-mode segment is aimed to generate a phase difference of 180°. Under this assignment, the radiative electric-fields are all in-phase on the antenna aperture, thus realizing the expected high-gain radiation. The design method of this hybrid resonant antenna is deeply investigated based on the dispersion curves of the EH₁-mode and TEM-mode. For verification, the presented antenna with ten units is practically implemented and measured. The obtained results indicate that the desired horizontally-polarized radiation with a high-gain of 13.6 dBi is well maintained in the H-plane. In final, the presented antenna is employed to form an eight-element phased array. The designed phased array is fabricated and tested, showing that the array has realized a beam scanning angle from – 40° to + 30°.