Inhibitory control may be vital in elite sport. The authors examined the link between athletic expertise, inhibitory control, and sport performance in a two-part quasi experiment. Inhibitory control was indexed using the Stop-Signal Task, athlete expertise was categorized on literary recommendations, and sport performance was assessed using athlete and coach ratings. Study 1 examined cross-sectional and longitudinal patterns of inhibitory control across athletic expertise. Study 2 investigated whether the inhibitory control–sport performance relationship was moderated by expertise. Study 1 showed that expertise was linked to greater inhibitory control cross-sectionally and longitudinally. Study 2 revealed that expertise was related to superior performance on the Stop-Signal Task and athlete and coach performance ratings, and this relationship was moderated by athletic expertise. Inhibitory control relates to sport performance, increases with greater athlete expertise, and develops longitudinally. Long-term participation in sport may bring about changes in inhibitory control, which may lead to improved sport performance.