The present study was a randomised controlled trial investigating the effectiveness of the Mindfulness-Acceptance-Commitment (MAC) approach compared to traditional Psychological Skills Training (PST) for the mental health and sport performance of female collegiate athletes. Two hypotheses were proposed: (a) participants in the MAC group would demonstrate reduced behavioural issues, emotional distress, and psychological symptoms, and increased athletic performance when compared to those in the PST group; (b) MAC participants would exhibit reduced emotion dysregulation and increased psychological flexibility and dispositional mindfulness, compared to PST participants. Participants included 18 National Collegiate Athletic Association Division III female student athletes who were randomly assigned into either the MAC or PST group based upon pre-intervention levels of distress; and were assessed pre-intervention, post-intervention, and at 1-month follow-up. A mixed-model ANOVA analysis revealed that the MAC effectively reduced Substance Use, Hostility, and Emotion Dysregulation over time when compared to the PST group. Several within-group differences also emerged, as MAC participants demonstrated reduced Generalised Anxiety, Eating Concerns, and Psychological Distress, as well as increased psychological flexibility from post-intervention to one-month follow-up. As per coach ratings, MAC participants also evidenced improved sport performance from pre-intervention to post-intervention. Results suggest that the MAC is an effective intervention for the mental health and sport performance needs of female collegiate athletes.