In this paper, an adaptive fuzzy sliding-mode controller (AF-SMC) based on fractional calculus for uncertain chaotic nonlinear systems were proposed. Three fuzzy logic systems were designed to approximate the unknown system functions and the switching term of SMC, respectively. Stability of the closed-loop system was proved and adaptive laws for the tuned parameters were obtained by using Lyapunov arguments. Numerical simulations are done on the chaotic nonlinear gyroscope system and results show that the proposed fractional order controller is effective and feasible.