In this paper, a compact tunable microstrip patch antenna with Co2Z hexaferrite substrate ($μ$r=15, $ε$r=12) that resonates on 360 MHz has been designed and fabricated, of which the frequency can be tuned by ∼2.5/1. Compared with an identically sized patch antenna with dielectric material Rogers TMM13i ($μ$r=1, $ε$r=12) operating at 1120 MHz, the magnetic antenna on the Co2Z substrate exhibited a high bandwidth of 23% at 360 MHz, which is much higher than 0.95% for the nonmagnetic antenna on the TMM13i substrate. In addition, the resonance frequency of the patch antenna on Co2Z can be tuned from 360 MHz to ∼900 MHz, or a tunability of 2.5/1, via the bias magnetic field. The combined size miniaturization, significantly enhanced bandwidth and significant tunability makes these Co2Z substrates with similar relative permeability and permittivity promising for future compact antenna substrates.