Although Spectral and Pseudospectral methods have been used in a wide range of optimal control applications, to date, most of the literature uses these methods in a non-robust sense without considering possible dynamic deviation (uncertainties) from the nominal model. This study applies a recent robust approach for spectral and pseudospectral methods to a wave energy converter, considering structured uncertainty in the dynamical system. The results show that the robust approach gives better worst-case performance than an equivalent non-robust approach. Additionally, when structured uncertainty is considered in the dynamical system, the results show that the absorbed energy, obtained with the robust approach, is always positive. Finally, the advantages of this new approach are commented.