Tower cranes are typical underactuated system commonly used on land as a large transport device. Moreover, workers regularly move loads and adjust the length of the rope simultaneously to improve the efficiency of crane transport. However, most of these methods require accurate velocity feedback and do not take into account the lifetime of the driving motor and variable rope length, leading to frequent safety accidents in practical working conditions. Therefore, in this paper, we propose an amplitude saturated nonlinear output feedback controller for five-degree-of-freedom (5-DOF) underactuated tower cranes without velocity measurement. Firstly, all studies are based on a variable rope length tower crane system. Secondly, an amplitude saturated nonlinear output feedback controller without velocity measurement is designed. Furthermore, Lyapunov theorem and LaSalle’s invariance principle are used to prove the asymptotic stability of the closed-loop system at the target position. Finally, we experimentally demonstrate the effectiveness of the proposed controller.