Athletes experience unique stressors that have been indicated to compromise their mental wellness and sport performance, yet they underutilize mental health services. Indeed, very few mental health interventions for athletes have been developed to fit sport culture, and well-controlled mental health outcome research in athlete populations is warranted. In this randomized controlled trial, a sport specific optimization approach to concurrent mental health and sport performance (The Optimum Performance Program in Sports; TOPPS) was examined. Seventy-four collegiate athletes (NCAA = 42; club = 11; intramural = 21) formally assessed for mental health diagnostic severity were randomly assigned to TOPPS or campus counseling/psychological services as usual (SAU) after baseline. Dependent measures assessed general mental health, mood, mental health factors affecting sport performance in training, competition and life outside of sports, days using substances, sexual risk behaviors, happiness in relationships, relationships affecting sport performance, and contributions of relationship to sport performance. Intent to treat repeated measures analyses indicated that participants in TOPPS consistently demonstrated better outcomes than SAU up to 8-months post-randomization and for mental health/substance use measures, particularly when diagnostic criteria were most severe. Recommendations are provided in light of the results to assist sport-specific mental health intervention development and implementation within athlete populations.