This paper presents a robust backstepping adaptive controller to overcome the overparameterization problem in adaptive control of nonlinear discrete-time systems. It is shown that the proposed controller can guarantee the global boundedness of the states of the whole adaptive system in the presence of time-varying parametric and nonparametric uncertainties. It can also ensure that the tracking error falls within a compact set whose size is proportional to the magnitude of the uncertainties and disturbances.