Singular perturbation theory is found to be a good approach to obtain a reduced order model in large-scale systems which suffer from big dimension and ill conditions for its state matrix. This article presents the use of a single fuzzy sliding mode controller designed for the slow component of a singularly perturbed system. Choosing the sliding surface parameter for a sliding mode controller in this case is a challenging problem. A fuzzy logic algorithm is used to obtain a nonlinear sliding surface to obtain better-closed loop performance. The validity of the proposed approach is verified by example.