A miniaturized V-band leaky-wave antenna (LWA) with circular polarization and backward-broadside-forward radiation based on a modified half-mode substrate integrated waveguide (M-HMSIW) is presented. The proposed M-HMSIW structure employs broadside coupled complementary split ring resonators to replace metallic vias, resulting in low-cost and fully-planar fabrication advantages over conventional HMSIWs. Each unit cell of the proposed LWA consists of an M-HMSIW in combination with two horizontal stubs and a cross-shaped complementary electric LC slot to provide a proper circular polarization with a composite right/left-handed property. Using this structure, the balanced condition can be obtained for the unit cell; hence a continuous backward-to-forward scanning, including broadside, is achieved. As a result, the proposed LWA with a radiator length of only 3.8λ0provides wide-angle beam scanning from − 53° to + 54° over the frequency range of 61.2 GHz to 73.4 GHz, while maintaining an excellent circular polarization between − 25° and 25°. The maximum gain of the LWA is 11.1 dB which is satisfactory, considering its compactness. The antenna’s performance is experimentally verified, and close agreement between the simulations and measurements is observed.