A Multiple Inputs Multiple Outputs (MIMO) antenna with a compact dimension of 0.28 lambda(0) x 0.36 lambda(0) for ultra-wideband (UWB) spectrum applications has been proposed, where, lambda(0) is the free space wavelength at the resonating frequency of 3.34 GHz. The proposed work consists of two identical radiating antenna elements and a modified T-shaped ground structure with a loaded rectangular slot. The modified T-shaped structure greatly affects impedance matching and electromagnetic field distribution. Due to that, the impedance bandwidth, isolation, compactness, and other MIMO parameters are also enhanced. The proposed antenna confirms a measured UWB frequency of 3.0- 11.66 GHz. The antenna isolation greater than 20 dB throughout the working spectrum is achieved. The results further signify that the antenna displays good MIMO performance with respect to envelope correlation coefficients (ECC), diversity gain (DG), channel capacity loss (CCL), and gain. The ECC value of less than 0.01, diversity gain above 9.98 dBi, peak gain of 3.52 dBi, and CCL lesser than 0.25 bits/S/Hz are achieved. The group delay and phase response are also studied for ensuring distortion-less signal transmission under broad impedance bandwidth.