In this paper, we investigate the use of widely linear processing in multiple-input multiple-out (MIMO) systems employing filter bank based multi-carrier with offset quadrature amplitude modulation (FBMC/OQAM). The concept of a twostep receiver combining linear processing and widely linear processing is presented. In the first step we cancel the intrinsic interference that prevents us from exploiting the benefits of widely linear processing. Two ways of estimating the interference components are developed and compared. In the second step, a widely linear MMSE receiver is employed taking into account the residual interference. A significant gain over the linear processing based receiver is demonstrated via numerical results.