Objective: The present study aimed to determine the effect of mental toughness on improving the performance and retention of the badminton long-serve skill in adolescents.

Materials and Methods: This study was applied in purpose and quasi-experimental in design, conducted using a pretest–posttest design. To achieve the research objectives, 24 right-handed female participants aged 16–18 years were selected via convenience sampling. Based on the pretest scores of the Scott and Fox long-serve test and the mental toughness questionnaire, participants were divided into two groups: high mental toughness (n = 12) and low mental toughness (n = 12). Each group completed six training sessions, performing three blocks of 10 trials of the criterion task per session, with a five-minute rest between blocks. Immediately after the final session, a posttest was conducted, followed by a retention test 24 hours later. Data were analyzed using the Shapiro–Wilk and Levene tests, and to examine the effect of training and between-group differences, paired-sample t-tests, independent-sample t-tests, and mixed ANOVA were used.

Results: The results indicated that both groups showed significant improvements from pretest to posttest as well as in the retention of the badminton long-serve skill. However, the high mental toughness group demonstrated superior performance in both the posttest and retention test compared to the low mental toughness group.

Conclusion: High mental toughness positively influences the performance and retention of the badminton long-serve skill in adolescent girls. These findings highlight the importance of psychological characteristics in improving motor skill performance and retention.