This paper studies control designs for a class of nonlinear descriptor systems under state undecomposed status and presents a number of new results on the stabilization, H∞ control, and robust adaptive control. It is shown that under a suitable state feedback, two sufficient conditions of impulse-free can be established for the resulted closed-loop system. Using the established conditions, the stabilization problem is then discussed for the nonlinear descriptor system, and a stabilization control design procedure is presented; on the basis of which, an admissible H∞ controller and an admissible robust adaptive controller are designed for the system with external disturbances and/or parametric uncertainties. Simulation results on a nonlinear descriptor circuit system show the efficiency of the controllers proposed in this paper. Copyright © 2012 John Wiley & Sons, Ltd.