The purpose of this study was to investigate the relationships between mindfulness, alexithymia, burnout, and performance efficacy among athletes by means of a longitudinal survey. Participants were 125 university athletes (74 men, 50 women, 1 unknown gender; mean age: 19.84 years, SD = 1.04) who completed a survey comprising the Athlete Mindfulness Questionnaire, Sport Alexithymia Scale, Burnout Scale for University Athletes, and Psychological Performance Efficacy Scale (on which they assessed both themselves and a teammate) at three time points separated by two-month intervals. Mindfulness was found to be negatively correlated with burnout, both directly and in an indirect relationship mediated by alexithymic tendencies; mindfulness was also positively and directly associated with self-evaluation of performance, and indirectly positively associated with performance as evaluated by a teammate, via burnout. Structural equation modeling showed that the hypothesized model represented an acceptable fit to the data, based on several indices. Our findings suggest that mindfulness may help to enhance performance and reduce future burnout among athletes.