In this manuscript, a cascaded filtering antenna structure is proposed. To realize this concept, we leverage the cavity-backed slot antenna as a foundation and take advantage of cutoff frequencies of waveguides to achieve it in the millimeter-wave (mmW) bands. The working principle and parameter analyses are introduced. Subsequently, we present the fabrication process and measurement results, which are then compared with simulation results. The obtained results demonstrate acceptable performance in terms of reflection coefficients and radiation patterns. Furthermore, by comparing our proposed antenna with published works, we highlight its advantages in terms of out-of-band rejection and similar beam width in E-plane and H-plane.