This paper introduces a slotted antenna configuration integrated within a millimeter wave substrate. The antenna is meticulously crafted to function across two distinct frequency ranges: 31.4 and 38 GHz. The individual antenna element comprises a substrate-integrated waveguide (SIW) cavity with longitudinal slots etched each in the ground plan and radiating patch, respectively. These slots are designed to resonate at frequencies of 31.4 and 38 GHz. The simulated outcomes demonstrate that the antenna showcases excellent performance in relation to return loss and radiation pattern within the dual-band range of 31.4 and 38 GHz, respectively. The return loss exceeds −10 dB (−26.1528 dB @ 31.4 GHz and −21.3605 @ 38.0 GHz) and a gain of 9.0809 dBi is achieved with a suitable bandwidth range of nearly 2.0074 GHz (from 30.6926 to 32.7000 GHz) and nearly 1.6673 Ghz (from 37.0714 GHz to 38.7387 GHz), respectively. The antenna structure is constructed using Roger RT5880 substrates, possessing a permittivity of 2.2 and a loss tangent (tan δ) of 0.002. Hence, this research article presents a novel SIW antenna arrangement that provides the capability of operating in two frequency bands, maintains a compact form factor, and exhibits an optimized structure.