This thesis deepens understandings of the relationship between friendship and mental health in the lives of teenage girls by positioning them as knowers. Grounded in social constructionism and feminist standpoint theory, I use reflexive thematic analysis to analyze semi-structured interviews conducted with nine teenage girls in Ontario, Canada to explore the knowledge they generated through caring for one another's mental health. Teenage girls' mental health is inextricably tied to experiences of power, with oppressions acting as sites of power diminishment while friendships act as sites where power is created and nurtured. My findings are conceptualized in three components: the frame is Power, the context is a Toxic Environment (Adultism, Capitalism, and Patriarchy), the knowledges are Power-full Friendships (Effective Support, Therapeutic Values, and World Crafting) and Self-Becoming (Self-Determination, Self-Knowledge, and Access to resources). This understanding has implications for improving mental health systems, social work empowerment models, and subverting structuralized oppressions.