Physical activity occurring through organized sport has been positioned as an engaging manner not only to prevent chronic-degenerative diseases but also to promote healthier societies. However, there is a lack of evidence linking competitive sport participation in the club environment in promoting youth athletes’ psychosocial development and mental health. Thus, this study aimed to analyze the effects of age, sport type, and training experience on the psychosocial development and mental health of youth Brazilian club athletes. Participants were 220 male adolescent athletes (Mean =14.09 years; SD = 2.21) from individual and team sports. Instruments included the Portuguese Youth Experience Survey for Sport (P-YES-S) and the Portuguese Mental Health Continuum – Short Form (P-MHC-SF). Correlation and multilevel linear regression analyses were performed. The results indicated a moderated correlation between both questionnaires. For the P-YES-S, model effect estimations showed variation for age in the Personal and Social Skills dimension and variations for training experience in the Cognitive Skills and Negative Experiences dimensions. For the P-MHC-SF, model effect estimations showed variation for age in the Emotional Well Being dimension and variation for sport type in Social Well Being and Psychological Well Being dimensions. More research is needed to continue examining how characteristics of sport participation are related to psychosocial development and mental health.