In this paper, a 2-by-1 MIMO reconfigurable antenna using Quarter Mode Substrate Integrated Waveguide (QMSIW) is introduced for wireless communication application. By combining three antenna techniques, the proposed design has a compact size due to QMSIW cavity, operation frequency flexibility by using varactor diodes, and channel capacity improvement from MIMO setup. The antenna is integrated with varactor (MA46H120) to tune its operating frequency from 2.35 to 2.55 GHz (ISM band). The antenna has a high isolation level (below -15 dB), and a peak gain of around 2.3 dBi across the tuning frequency range. The agreement between measured and simulated results shows successful performance and characteristics satisfying various MIMO parameters requirements.