Positive developmental outcomes among youth living in poverty have rarely been studied. Despite numerous risk factors, it is important to understand the factors that contribute to positive developmental outcomes among youth in poverty. Using the Self-Determination Theory framework, this two-wave longitudinal study investigated the contribution of basic psychological needs of autonomy, competence, and relatedness to positive developmental outcomes of prosocial behavior and positive affect among 225 youth living in poverty in Italy. Results suggest that overall, prosocial behavior was positively predicted by autonomy, while positive affect was positively predicted by competence. Moderator analyses showed that the satisfaction of the need of relatedness predicted prosociality for girls and immigrants. For girls, the fulfilling of this need also predicted positive affect. The importance of each psychological need to different positive outcomes was shaped by adolescents' economic condition, immigrant background, and gender. The implications for further research and practices are discussed.