Neuroscientific findings suggest that observing temporally occluded actions evokes a mental simulation of the occluded action part. This action simulation may involve corresponding motor programs in the observer and is suggested to run in real time. The present study aimed to investigate whether real-time action simulation relies on effector-specific motor representations. Our participants watched transiently occluded actions performed either with the arms or the legs and had to predict the action course after occlusion. Participants also responded to the task with a movement involving either their arms or legs. Simulation performance broke down when the observed effector and the moved effector corresponded. In contrast, simulation was intact when the effectors did not correspond. The results are in line with previous research and extend it by showing that interference effects can occur within the real-time course of action simulation. Furthermore, shared representations between action simulation and action execution are effector specific.