In this paper, a substrate integrated waveguide (SIW) cavity-backed slot antenna is presented for a dual-frequency operation. In the proposed design, a pair of triangular-complementary-split-ring slots is used for radiation. These slots are found useful to excite narrowly spaced hybrid-modes in the SIW cavity, which improve the antenna performance significantly. The proposed antenna is prototyped on a low-cost substrate using printed-circuit-board (PCB) technique and experimentally tested. The tested results describe that antenna operates in two frequency bands, ranging from 8.50 to 8.70 GHz (200 MHz) and 13.03–13.84 GHz (810 MHz). The antenna exhibits the resonant frequencies of 8.6 GHz and 13.3 GHz with peak gain values of 5.1 dBi and 6.3 dBi, respectively, covering the X and Ku-bands. Moreover, the tested results agreed well with the simulated one, obtained from CST and HFSS simulators. The proposed antenna offers attractive features such as unidirectional radiation patterns with high gain and planar integrability. The total occupied volume of the proposed design including feedline, in terms of λo is 0.86λo × 1.3λo × 0.05λo. © 2018 Elsevier GmbH