Pathological tremor is a common neuromuscular disorder that affects millions of people around the globe. This disease largely affects the quality of activities of daily living such as drinking, eating, and writing, such that patients suffering from pathological tremor often have a problem in self-care. This work presents a wearable elbow exoskeleton for tremor suppression (WEETS), which offers an alternative assistive technology to the conventional treatments based on surgery and drug therapy. The WEETS system uses a novel configuration and controllable rotational semi-active actuator (RSAA) based on magnetorheological fluid to suppress the tremor in the elbow joint. The RSAA is characterized by its compact structure, lightweight and enough output torque (about 3.5 Nm). The performance of the WEETS system is validated with simulations and a series of experiments. The results show that the WEETS has the capability to attenuate the elbow tremor regarding the magnitude of angular velocity and acceleration by 61.55% and 61.68%, respectively. Furthermore, for better evaluation of the WEETS system, an instrument based on voice coil actuator is developed to generate mechanical signals simulating pathological tremors, which is a novel method to show the validation of the exoskeleton system for tremor suppression. Overall, the results from the experimental setup and simulations confirm the effectiveness of WEETS on tremor suppression.