In this letter, a novel transparent substrate integrated waveguide (SIW) cavity-based slot antenna operating in millimeter-wave band has been presented for fifth generation wireless communication application. Different from the traditional opaque SIW antennas, the proposed antenna is composed of transparent conductive mesh with high conductivity characteristics acting as radiation element and ground, and transparent polyethylene terephthalate material used as substrate. By removing a few metallic vias from the SIW cavity, the TE <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">103</sub> mode is well generated. The introduction of several slots etching on the radiation element results in multiple hybrid resonances, and thus the proposed antenna operates in a band of 24.31–27.81 GHz, with a peak gain of 7.8 dBi at 26.5 GHz. The prototype of the designed antenna is fabricated, and the simulated and measured results are given to show that the proposed antenna has good optical transparency and both the cross-polarization ratio and front-to-back ratio are better than 20 dB within the operating band.