With physiological aging, appears a deterioration of the ability to retain motor skills newly acquired. In this study, we tested the beneficial role of motor imagery training to compensate this deterioration. We tested four groups: young control group (n=10), elderly control group (n=10), young mental-training group (n=13) and elderly mental-training group (n=13). In pre- and post-tests, the participants performed three trials on a dexterity manual task (the Nine Hole Peg Test), commonly used in clinic. We recorded the movement duration as a factor of performance. Each trial, including 36 arm movements, consisted in manipulating sticks as fast as possible. The control groups watched a non-emotional documentary for 30min and the mental-training groups imagined the task (50 trials). First, we observed a speed improvement during the pre-test session for all groups. Immediately after viewing the movie (post-test 1), the young control group showed a preservation of motor performance in comparison to the performance measured before the break (pret-test 3), while the young mental-training group improved performance after motor imagery practice. For the elderly, the control group showed a deterioration of motor performance at post-test 1, attesting a deterioration of the ability to retain motor skills with aging. Interestingly, the elderly mental-training group showed a preservation of motor performance between the pre-test 3 and the post-test 1. The present findings demonstrate the beneficial role of mental training with motor imagery to retain the performance improvement following physical practice in the elderly. This method could be an alternative to prevent the deterioration of motor skills.