In this paper, the joint actuator fault estimation (AFE) and the wheeled mobile robot (WMR) localization under the Round-Robin protocol (RRP) problems are concerned. In order to complete the joint AFE and the WMR localization, a nominal joint system is constructed, which consists of the drive subsystem and WMR localization subsystem. In the drive subsystem of the WMR, the DC motor is used as an actuator to drive the WMR. When the faults occur, the performance of the actuator will be degraded, and the mobility of the WMR will be affected. In order to maintain a satisfactory mobility of the WMR, the faults need to be estimated timely such that some appropriate decisions or remedies can be made. In the WMR localization subsystem, for saving the network resources, the RRP is introduced to schedule the transmission of sensor measurements used for the WMR localization. The purpose of this paper is, by designing a time-varying filter for the constructed joint nominal system, to ensure the filtering error to meet the given [Formula: see text] performance requirement, such that the joint AFE and the WMR localization can be achieved simultaneously. Specifically, the sufficient condition is derived first and then the desired filter gain is designed by the recursive linear matrix inequality technology. Finally, a simulation experiment is conducted to certify the usefulness of the proposed algorithm.