This paper presents a novel miniaturized CPW fed UWB antenna. The compactness of the antenna is achieved by using modifications in ground plane of the CPW feed structure and the radiator design. The volume of this proposed antenna is 18 × 16 × 1.6 mm3. This antenna is used to make two novel miniaturized 2 × 2 MIMO antenna arrays of dimension 32 × 18 × 1.6 mm3 and 34 × 18 × 1.6 mm3 for UWB applications. These MIMO antenna arrays with modified ground structure are made by lateral and orthogonal positioning of the proposed UWB antenna with itself. The proposed UWB antenna and other two MIMO antennas cover entire UWB range 3.1–10.6 GHz. The proposed MIMO antennas are uniplanar having satisfactory performance in terms of return loss, isolation, envelope correlation coefficient (ECC) and diversity gain.)