This paper presents an output feedback sliding mode control algorithm for linear MIMO systems with mismatched parameter uncertainties along with disturbances and matched nonlinear perturbations. A scheme of the output-dependent integral sliding surface is proposed and a control law is then designed to satisfy the reaching and sliding condition. Through utilizing H _∞ control analytical technique, once the system is in the sliding mode, the proposed algorithm can guarantee robust stabilization and sustain the nature of performing disturbance attenuation in terms of an algebraic Riccati equation. Finally, the feasibility of our proposed algorithm is illustrated using a numerical example.