Conventional orthogonal frequency division multiplexing (OFDM) systems use cyclic prefix (CP) to protect signal from the multipath channel induced distortions. However, the presence of CP could greatly decrease the effective data rate. In this paper, an interference cancellation scheme based on the generalized sidelobe canceller (GSC) principle is proposed for interference suppression of CP-free multiple-input multiple-output (MIMO) OFDM systems. An associated reduced complexity implementation based on the partially adaptive (PA) scheme is also proposed by exploiting the structural information of the signal and interference signature matrices. As well, we study sampling error in the proposed system. Under the block transmission model, a simple sampling error estimation method is proposed. Whenever sampling error is known, the proposed GSC equalizer can be directly applied based on the timing offsetted system model. Simulation results show that the performance of the proposed solution is almost identical to that obtained by the conventional CP-based MIMO-OFDM system under either the synchronous or asynchronous scenario.