In this paper, a novel design of half-mode substrate integrated waveguide (HMSIW) cavity based antenna is presented for dual-frequency application in Ka band (26-40 GHz). Two HMSIW cavities are placed side by side and are excited through the help of inductive coupling window followed by a section of HMSIW line. As a result, the cavities are excited at TE110 HM mode and the open end dielectric aperture of the HMSIW cavity starts radiating into free space. The two HMSIW line are connected to the input SIW feeding line with the help of a SIW to HMSIW power divider. The proposed antenna resonates at 26 GHz and 29 GHz while maintaining a compact design configuration which makes it suitable for application in LMDS frequency band. © 2017 IEEE.