Essential tremor, the most common pathological tremor, is assumed to originate in the central nervous system. It can result in functional disability because the tremors obstruct movement. We have developed a soft exosuit to assist essential tremor patients that provides a comfortable, unobtrusive and soft interface to the human body, and evaluated whether it can constrain joint movement and suppress tremors. We developed a prototype cable-driven exosuit based on three-point fixation that restricts joint motion only when necessary. Tremors were simulated in healthy test subjects using functional electrical stimulation. The experimental results show that the tremor intensity obtained with the exosuit in constrained mode was approximately 62% of that obtained in unconstrained mode. These results show that the cable-driven soft exosuit effectively suppressed joint motion in patients with simulated essential tremor. We also demonstrated that the exosuit could switch between constrained and unconstrained modes.