A dual-fed low-profile self-diplexed slot antenna is proposed for 5.2/5.8 GHz applications. The antenna mainly comprises a half-mode substrate integrated waveguide (HMSIW)-based cavity, loaded with a slot and microstrip feedlines. A radiating slot is etched on the upper metal cladding of the HMSIW cavity which splits the cavity into two sections. When each section is excited by using two orthogonally placed feedlines, it generates two frequency bands around 5.2 and 5.8 GHz. By finely tuning the antenna dimensions, a very high isolation of better than 30 dB is realised between the input-ports. Thereby, the proposed antenna exhibits the self-diplexing property. Finally, the proposed antenna is fabricated and the experimentally tested. The experimental results show a close mutual agreement with simulations. Moreover, the antenna shows unidirectional, stable and similar radiation characteristics at both the operating frequencies with maintaining planar configuration. The proposed design provides an easier, compact and a more cost-effective solution for RF front-end components and substitutes the conventional complex diplexer networks. © The Institution of Engineering and Technology 2018