In this paper, a robust adaptive control method for a class of fourth-order systems is proposed. The used structure for this controller is a combination of decoupled sliding mode approach and feedback linearization technique. The decoupled sliding mode is applied to guarantee the sliding condition, and by applying the feedback linearization method, a linear control law with adaptive coefficients is employed. The final control effort is defined as the weighting summation of the decoupled sliding mode and feedback linearization controllers. Then, the controller coefficients are optimized using the multi-objective genetic algorithm. Finally, to show effectiveness of the proposed approach, it is applied to handle the cart-pole, ball-beam, and ball-wheel systems and the results are compared with those reported in the literature.