Limb immobilization paradigms are increasingly used to investigate changes in brain plasticity and support potential rehabilitation techniques that might help counteract motor impairments. Yet, it remains unclear how unilateral arm immobilization may influence the sensorimotor representation and functional output for both arms. Using a randomized crossover design, 14 participants underwent a baseline test, followed by two experimental conditions separated by 1 week: a right (dominant) arm immobilization phase over a period of 8 hr and a no-immobilization (or control) phase also lasting 8 hr. Before and after each condition, participants were tested on a hand laterality judgment task to assess changes in sensorimotor representation of the hands, followed by an out-and-back reaching motor task measuring changes in spatiotemporal components of motor actions. Data from the hand laterality judgment task revealed that participants were faster at identifying right-hand pictures after the control phase, but such improvement was not observed after the immobilization phase, with no effect of immobilization for pictures depicting the overused left hand. Results from the reaching motor task revealed that the right-arm movement planning component was altered after immobilization, whereas there was no effect for the overused left arm. Altogether, these findings demonstrate that an 8-hr period of unilateral immobilization affects sensorimotor representation and functions of the corresponding limb, but not of the overused, nonimmobilized hand. (PsycINFO Database Record (c) 2018 APA, all rights reserved).