In this paper, the fault detection problem is investigated for a class of discrete-time switched singular systems with time-varying state delays. The residual generator is firstly constructed based on a switched filter, and the design of fault detection filter is formulated as an H 1 filtering problem, that is, minimizing the error between residual and fault in the H 1 sense. Then, by constructing an appropriate decay-rate-dependent piecewise Lyapunov function and using the average dwell time scheme, a sufficient condition for the residual system to be regular, causal, and exponential stable while satisfying a prescribed H 1 performance is derived in terms of linear matrix inequalities (LMIs). The corresponding solvability condition for the desired fault detection filters is also established via LMI approach. Finally, a numerical example is presented to show the effectiveness of the developed theoretical results.