An actuator fault diagnosis method is presented in this paper for a class of time-delayed nonlinear systems via the use of adaptive updating rules. The considered system is represented by a dynamical state space model where the time delays are embedded in the state vector. Model parameters are not perfectly known which leads to consider norm bounded uncertainties. An adaptive fault diagnosis observer is designed, where the Lyapunov stability theory is used to obtain the required adaptive tuning rule for estimation of the nonlinear actuator fault. A simulated numerical example is included to demonstrate the effectiveness of the proposed approach.