This letter presents a monopole antenna with a magneto-dielectric material and its multiple-input-multiple-output ( MIMO) applications. The proposed antenna fed by a 50-Omega coaxial line occupies a compact volume of 9.5 x 3 x 1.2 mm(3) and the parameters of the magneto-dielectric material as a supporter are epsilon' - j epsilon '' = 3.86 - j0.032 and mu' - j mu '' = 1.23 - j0.25 at the resonant frequency. The bandwidth is 850 MHz (3.38-4.23 GHz) at S(11) < -10 dB, and the measured maximum gain is 5.57 dBi at 3.8 GHz. For evaluations of the MIMO application, the antenna has been measured in both the spherical and reverberation chamber. The microwave studio (MWS) simulation is employed for optimizing the design parameters and the simulated results are well agreed with those of the measured one.