SummaryThis study deals with the state observer design for a class of linear time‐delay distributed parameter systems (DPSs) modeled by a parabolic partial differential equation (PDE) via mobile sensors. Initially, under the assumption that the spatial domain is decomposed into multiple subdomains according to the number of mobile sensors, the estimation scheme including a state observer and the guidance of mobile sensors is proposed for the linear time‐delay DPS. Then, by using Lyapunov direct technique and the projection modification algorithm, a design of the state observer plus mobile sensor guidance laws is developed, such that the resulting state estimation error system is exponentially stable and the mobile sensor guidance can improve the transient response of state estimation error. Finally, numerical simulations are presented to show the effectiveness of the proposed method.