In this article, we consider an output feedback control problem of switched stochastic nonlinear systems under sampled-data, where the switching converts to asynchronous switching if the switching occurs within the sampling interval. We first construct the output feedback sampled-data controller by the back-stepping method. And the limiting conditions of the sampling period are obtained based on the average dwell time method. We show that the closed-loop system is globally mean-square asymptotically stable and has a weighted L 2 -gain. Moreover, our theoretical results are applied to two numerical examples to demonstrate the validity of the proposed method.