The sport commitment model specifies various contributors to sport commitment (Scanlan et al., 1993, 2016). Among these contributors is social constraints, the social expectations or norms that create perceptions of obligation to remain in sport. This construct has been inconsistent in predicting commitment, which is surprising considering the importance of social agents (e.g., teammates, coaches) to sport involvement. A more complex relationship between social constraints and sport commitment may exist, whereby prediction requires athletes to possess motivation to control how others view them, known as impression motivation (Leary & Kowalski, 1990). The purpose of this study was to explore whether impression motivation moderates the relationship of social constraints with sport commitment. University athletes (N = 262; M age = 20.0 years) provided demographic information and completed established assessments of impression motivation (four components) and sport commitment constructs. Eight hierarchical multiple regression models were run predicting enthusiastic and constrained commitment, respectively (four models each). One model predicting enthusiastic commitment supported the moderation hypothesis. The interaction of social constraints and self-development impression motivation predicted a small amount of variance beyond the main effects (R2–change = .02, p < .05). Simple slopes suggested that as self-development impression motivation increases, the positive relationship of social constraints with commitment increases. In the context of limited support for our general hypothesis, the findings suggest that self-development impression motivation may be informative in understanding sport commitment. Further research is needed to clarify how social relationships and impression motivation may interface to influence sport commitment.