Muscle vibration (MV) has been suggested as a useful non-pharmacological approach to control spasticity. Armeo Power® (AP) is a robotic exoskeleton for rehabilitation allowing early rehabilitation treatment. The objective of our study was to determine whether AP training coupled with MV applied on antagonist muscles of the spastic upper limb (UL) can reduce the spasticity of agonist muscles. We enrolled 20 chronic post-stroke patients, who underwent 40 daily sessions of AP training. Ten subjects (group-A) received muscle MV (on triceps brachii, deltoid, and supraspinatus), whereas the other 10 (group-B) underwent a sham vibration.