Abstract: The relationship between coach- and peer-created motivational climates and Positive Youth Development is largely unexplored. This is especially true for the latter and in particular with regard to disadvantaged girls. The present study was designed to examine the relationships between perceived coach- and peer-created climates and reported developmental gains among disadvantaged girls participating in sports programmes, and to determine whether these relationships were moderated by personal characteristics. Two hundred young women aged between 12 and 22 completed a questionnaire which included the ‘Youth Experience Survey for Sport’ (MacDonald, Côté, Eys, & Deakin, 2012), the ‘Motivational Climate Scale for Youth Sports’ (Smith, Cumming, & Smoll, 2008), the ‘Peer Motivational Climate in Youth Sport Questionnaire’ (Ntoumanis & Vazou, 2005), and questions regarding participants’ socio-economic characteristics. Multilevel regression analyses were performed to take into account the hierarchical data structure. The analysis revealed that a mastery-oriented coach climate is a very strong predictor of perceived Positive Youth Development. This is based on both the number of developmental domains on which it had a significant impact and the explained variance based on the PRV values of the multi-level models. Unlike previous research on disadvantaged youth in general and disadvantaged girls in particular, the observed interaction effects did not show that disadvantaged girls necessarily gain more from their involvement in organised activities such as sport.