Two field studies investigate the role of self in the tendency of athletes to engage in claimed handicapping strategies during training (anticipatively claiming that handicaps may interfere with their performance). Study 1 tested the relationship between trait self-esteem and athletes’ engagement in claimed self-handicapping. As hypothesized, low physical self-esteem athletes claimed more handicaps than high physical self-esteem athletes. For stronger evidence for the causal role of the self, Study 2 tested whether securing athletes’ self-worth through self-affirmation would lead to decreased claimed self-handicapping by using a mixed model design that allows for both between-subjects (affirmation vs. control condition) and within-subject comparisons (before vs. after self-affirmation intervention). Self-affirmed athletes had decreased levels of claimed self-handicapping. Studies 1 and 2 also demonstrate that athletes engage in claimed self-handicapping during training, which could have deleterious effects on subsequent performance. Discussion centers on theoretical implications and applications for coaches, sport teachers, and sport psychologists.