In this paper, a folded slot-based multiple-input–multiple-output (MIMO) antenna design for Cube Satellite (CubeSat) applications is presented for the ultra-high frequency (UHF) band. A unique combination of a reactively loaded meandered slot with a folded structure is presented to achieve the antenna’s miniaturization. The proposed antenna is able to operate over a wide frequency band from 430~510 MHz. Moreover, pattern diversity is achieved by the antenna’s element placement, resulting in good MIMO diversity performance. The four elements are placed on one Unit (1U) for CubeSat dimensions of 100 mm × 100 mm × 100 mm. The miniaturized antenna design with pattern diversity over a wide operating band is well suited for small satellite applications, particularly CubeSats in the UHF band.