Varsity athletes face an array of stressors, including balancing academic obligations with athletic competitions. Student-athletes appraising a situation as a "challenge" or "threat" directly impacts coping responses. Objective: To investigate whether pre-season self-reported mental toughness and self-regulation strategies predicts post-season stress, mental health, group cohesion, and satisfaction in varsity athletes. Participants: Sixty-seven varsity athletes from a U-Sport Canadian university. Methods: Athletes completed pre- and post-season measures of mental toughness, emotion regulation, self-control, group cohesion, and satisfaction. Multiple mediation models were employed during analyses. Results: Pre-season emotion regulation was a significant mediator for the relationships between mental toughness and post-season ratings of perceived stress, perceived mental health, and group cohesion. Self-control was not a significant mediator. Conclusions: Emotion regulation plays a significant role in an athlete's experience of perceived stress, mental health issues, and their ratings of group cohesiveness. Research on student-athlete health may benefit from examining emotion regulation training techniques.