Past research has suggested that engaging in prosocial acts enhances the well-being of the helper, but does prosocial behavior benefit some individuals more than others? The current study implements a daily diary design to test associations between adolescents' daily prosocial behaviors toward relationally close others and mood. The main goal was to investigate whether daily help-giving has unique benefits for adolescents experiencing greater emotional distress. For 10 days, a diverse sample of youth (N = 99; Mage = 18.01) reported on their prosocial behaviors toward friends and romantic partners as well as their mood; depressive symptoms were assessed in a prior lab visit. Multilevel models showed that participants experienced increased positive mood on days that they were more prosocial, even when controlling for received support; this association was strongest among those reporting higher depressive symptoms. The findings highlight the unique benefits of prosociality in adolescents' daily lives, suggesting that everyday help-giving behaviors may fulfill social and emotional needs of depressed youth. (PsycINFO Database Record (c) 2019 APA, all rights reserved).