According to the sport-specific model of self-talk, self-talk dissonance occurs when a mismatch between gut feelings/impressions and self-talk creates discomfort and disrupts performance. The purpose of this study was to test the sport-specific model of self-talk’s dissonance hypothesis by examining the effects of self-talk on introverts (n = 28), who may be uncomfortable speaking their self-talk aloud, and on extraverts (n = 30). Each participant completed a dart-throwing target task using (a) overt and (b) covert self-talk in a counterbalanced order. Results of analysis of covariance indicated a significant interaction that supported the sport-specific model of self-talk’s dissonance hypothesis. Introverts performed better when using covert (private) self-talk, and extraverts performed better when using overt self-talk. The results of this research show that self-talk dissonance adversely affects performance and suggests that tailoring self-talk interventions by incorporating personal factors into intervention designs could enhance intervention effectiveness and performance outcomes.