This paper proposes the use of backstepping technique to address the stabilization problem of a dc-dc boost converter characterized by non-minimum phase property. The backstepping technique is used in conjunction with a disturbance observer to counteract the effect of model uncertainties and unmeasured disturbance. Therefore, not only does the developed controller achieve the task of stabilization, but it can also guarantee zero steady-state error in the presence of model uncertainties and unknown load. The asymptotic regulation of the composite controller follows from the integral action property of the disturbance observer. What is more interesting is that the composite controller can also compensate for the effect of control saturation during transients. This means that the proposed controller does not require an anti-windup scheme to maintain stable and graceful response during control saturation. Another feature of the proposed controller is its ability to achieve good tracking performances in response to a smooth voltage trajectory. Simulation and experimental tests have been conducted to investigate the performances of the proposed controller considering different operating conditions and different load types, including constant power load (CPL). The obtained results revealed that the proposed controller is able to achieve stable, accurate, and good response regardless of the load type.