The buck converter is an electronic device widely used in power electric applications. This converter has a nonlinear performance in consequence of the switching transistor effects which it uses. Implement a classic controller for this converter results very complex. Hence, fuzzy controllers are used to obtain a better steady state performance of the system. This paper presents a multi-objective optimization to ensure a steady state error (e <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">ss</sub> )<;0.03 and a ripple factor (Fr)<;0.03. We use the NSGA-II multi-objective algorithm, because this has an elitist approach that guarantees a great genetic diversity. The obtained results are validated using simulation of the algorithm obtaining a smaller e <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">ss</sub> and Fr than the previous works. This work represents an innovative contribution in the control of buck converters, due to the fact that there's no works in the literature that tunes this devices using NSGA-II.