A multi-input multi-output (MIMO) antenna is designed and discussed for multi-band applications. The constituent antennas are composed of four L-shaped elements and a ground plane. When placed beside each other to form a MIMO antenna, a T-bar shaped parasitic structure is also embedded between the antennas on the backside of the substrate to increase the inter-element isolation. The triple-band performance of the antenna is observed at 2.15–2.73 GHz, 3.1–3.9 GHz, and 5.04–6 GHz. The isolation level of more than 20 is seen over the operating frequency range. The fabricated prototype of the MIMO antenna size is very compact (20 × 40 mm), printed on the FR4 substrate. Based on simulation and experimental results, the proposed design is useful for WiMAX and WLAN applications.