In this study, we consider the stabilization of a class of cascaded nonlinear systems in strict feedback form with unknown dynamics and known relative order. The stabilization of the unknown system is achieved by a cascaded feedback design procedure that uses a backstepping-like approach. The unknown system functions are estimated using a phasor estimation approach using a single sinusoidal perturbation. The stability analysis shows the semi-global practical stability of the closed loop system and the practical convergence of the entire system to the origin.