ABSTRACT Youth can often be the subject of rude and discourteous behaviors in their sport setting, given their susceptibility to the social environments. Incivility refers to insensitive behavior that exhibits a lack of respect for others, namely, disrespectful and rude behaviors. Incivility is a significant issue in youth sport since it negatively influences teams and individuals. The present study aims to investigate 1) how incivility and psychological safety are associated with each other over time and 2) the influence of the initial value of psychological safety and the change in psychological safety on youth athletes’ well-being and social outcomes. Three-wave time-lagged data collection was employed, and the present study included 283 youth athletes who completed the survey three times. The hypotheses were tested in SEM with cross-lagged panel and growth latent curve modeling. The results showed that coach and teammate incivility were significantly associated with the change in psychological safety. In contrast, the initial value of psychological safety was a significant antecedent of the subsequent coach and teammate incivility, well-being, and social outcomes. Lastly, the change in psychological safety was significantly associated with youth athletes’ well-being and social outcomes. The findings suggest that incivility and psychological safety were reciprocally associated, and psychological safety rather than incivility was a significant predictor of youths’ well-being and social outcomes. The present study found a mechanism underlying the relationship between incivility, psychological safety, and essential outcomes (i.e., well-being and social outcomes) in youth sport.