This paper addresses robust adaptive sliding mode control for MIMO nonlinear systems in the presence of uncertainties and external disturbances. To achieve stability and performance, we propose a sliding mode control scheme with the design of a gain, whose gain is not constant and need to be adaptively updated. Unlike some existing methods for sliding mode control, no knowledge on the bound of uncertainty and disturbance is required to be known and only the fixed points and the dimensions of uncertain nonlinear systems are required to be known for control purpose. The effectiveness of the proposed controller design methodology is demonstrated by simulations.