Co2Z, a magneto-dielectric ferrite, has the potential to be used in the study of antenna miniaturization. The solidstate reaction method was employed to synthesize a series of Ba1.5Sr1.5Co2MnxFe23-xO41 (x = 0.0-1.0) hexaferrites in this paper. The crystal structure, microstructure, magnetic and dielectric properties were tested and investigated. The Mn3+ substitution did not introduce a second phase; however, it did influence the magnetic moments, super-exchange interaction, and electron hopping of the hexaferrite. Consequently, the magnetic and dielectric properties were altered, resulting in a decrease in losses. The hexaferrite exhibits superior magnetodielectric properties when x = 0.4, and the cut-off frequency exceeds 1 GHz. Additionally, both the magnetic and dielectric losses reach their minimum. The design and simulation of a rectangular patch antenna were conducted using Ba1.5Sr1.5Co2Mn0.4Fe22.6O41. The results indicate that the patch antenna size was effectively reduced, and the return loss S11 could reach -29.83 dB at 1 GHz. The proposed Mn3+ substituted Co2Z hexaferrite has the potential to be of value and use in the design of miniaturized antennas.