A fault detection(FD) and control co-design scheme is studied for discrete-time switched systems with time-varying delays under an arbitrary switching signal in a network communication. By using the average dwell-time scheme and a Lyapunov–Krasovskii functional(LKF), a delay-dependent sufficient condition is developed to ensure the resulting error system to be exponentially stable in the mean-square sense with an optimized H_∞ disturbance attenuation level. The solution of the parameters for the fault detection filter and controller co-design are characterized in terms of the feasibility of a convex optimization problem. A numerical example is given to illustrate the effectiveness of the proposed method.