Adolescence is a pivotal period of development with long-lasting implications for health and well-being. This chapter explores how families, schools, and societal structures influence adolescent health through interconnected and dynamic pathways. Drawing on ecological models and contemporary research, we examine the multifactorial determinants of adolescent health, including physical, mental, and social dimensions, and identify critical protective and risk factors. The chapter highlights the role of the family in shaping health behaviors and emotional regulation, the capacity of schools to serve as health-promoting environments, and the broader societal influences of social norms, media, and policy. Particular attention is paid to the interactions between these systems and their impact on equity, resilience, and developmental outcomes. We review integrated health promotion frameworks and evidence-based strategies that span multiple settings and emphasize the importance of adolescent engagement, inclusion, and empowerment. Barriers to implementation such as institutional inertia, stigma, and structural inequality are also discussed. The chapter concludes with actionable recommendations for cross-sector collaboration and system-level interventions to advance adolescent health. By positioning adolescents as co-creators of their own well-being, we underscore the importance of a coordinated, whole-society approach to supporting the health of current and future generations.