Pathological tremor is a kind of movement disorder that affects a wide range of patients with Parkinson's disease and essential tremor. Different from available clinical treatments for tremor, including drug and surgery therapy, a novel soft exoskeleton for tremor suppression (SETS) based on assistive technologies is proposed in this study. The SETS system is equipped with a controllable flexible semiactive actuator based on magnetorheological fluid. To overcome the drawbacks of traditional fluidic semiactive actuators, we devise a soft semiactive actuator that is a combination of cylinder-piston damper and elastic fluidic damper. The overall system is characterized with low mass, compact structure, comfortable wearability as well as real-time adjustability for tremor attenuation with varying intensity. The SETS can assist in suppressing tremor of wrist joint in three degrees of freedom. The prototype weighs about 255 g and can yield a maximum damping force of about 11 N. Simulation studies and experimental tests were carried out to evaluate the performance of the system. The results show that the SETS could reduce wrist tremor regarding magnitude of acceleration and angular velocity by 61.39% and 56.22%, respectively, which validate the manifest mechanical efficiency of this functional system.