We demonstrated the size reduction of axial-mode helical antenna based on Co2Z hexaferrite-glass composite. Axial-mode helical antenna was employed to provide reliable communication for unmanned aerial vehicle (UAV) applications. The conventional axial-mode helical antenna uses an air core or low dielectric material, resulting in large antenna size. To increase the miniaturization factor n = (μrεr)0.5, a Co2Z hexaferrite-glass composite was used as an antenna core. The 3-dimensional finite element method (FEM) simulation was performed to design a hexaferrite helical antenna and confirm the axial-mode operation at 2.44 GHz with gain of 2.0 dBi. The designed hexaferrite helical antenna showed 82% of volume reduction and good impedance matching compared to the air-core antenna. The axial-mode hexaferrite antenna was fabricated based on the designed structure and characterized in an anechoic chamber. The maximum gain of 0.541 dBi was measured with the pitch angle of 10° at 2.39 GHz. Also, a two-element axial-mode antenna array was designed based on the miniature hexaferrite antenna to further improve antenna gain. Maximum gain of 4.5 dBi at 2.43 GHz was simulated for the antenna array. Therefore, high gain and miniature antenna can be achieved with the combination Co2Z hexaferrite-glass composite and antenna design technology.