Natural disasters and times of crisis, such as the COVID-19 pandemic, are extremely stressful events, with severe mental health consequences. However, such events also provide opportunities for prosocial support between citizens, which may be related to mental health symptoms and interpersonal needs. We examined adolescents' prosocial experiences as both actors and recipients during the early stages of the COVID-19 pandemic and assessed whether these experiences were associated with indicators of mental health. Adolescents (N = 426; 78% female) aged 13 to 20 years (M  = 16.43, SD = 1.10; 63.6% White, 12.9% Hispanic/Latinx, 8.5% Asian, 4.2% Black, 2.8% Native American) were recruited across the US in early April of 2020. Participants reported on their COVID-19 prosocial experiences (helping others, receiving help) and mental health (depressive symptoms, anxiety symptoms, burdensomeness, belongingness). Multiple regression models indicated greater engagement in COVID-19 prosocial behavior was associated with greater anxiety symptoms and greater burdensomeness. Receiving more COVID-19 help was associated with lower depressive symptoms and higher belongingness. Findings highlight the importance of furthering our understanding of the nuanced connections between prosocial experiences and adolescents' mental health to help inform post-pandemic recovery and relief efforts. BACKGROUND The online version contains supplementary material available at 10.1007/s12144-021-02670-y.