The aim of this study was to evaluate the effects of motor imagery (MI: imagining the success or failure of a forehand or backhand shot) training according to an internal visual modality centred on the movement and the target to be reached on tennis performance. 66 young (M age = 12.1 years) players were randomly divided into three groups: control, failure MI or success MI, and performed 3 experimental phases. The pre-test consisted of performing 6 blocks of 5 forehand and backhand groundstrokes (sent randomly by a ball launcher towards the baseline) and a super tie-break. The acquisition phase consisted of 12 sessions, each including a standardized warm-up followed by 15 min of background rally in pairs. The participants of the MI group were instructed, after unprovoked errors on their part, to imagine performing the previous shot correctly (positive MI) or missing (failure MI). The post-test was identical to the pre-test. The efficiency score of shots and the number of errors committed at the pre- and post-test served as dependent variables. The results of this study indicate that participants in the success MI group performed better than the control and failure MI groups at post-test. The success MI, performed after errors, has positive effects on the quality of the shot and reduces the number of unforced errors of tennis players, while failure MI induces negative outcomes. The use of success MI, integrated in training session, is recommended.