With over 1.5 billion young people in the world who are between the ages of 10 and 25, ensuring the sexual and reproductive health of adolescents is essential for global health. Extensive variations exist in the prevalence of adolescent sexual and reproductive health behaviors and outcomes around the world. This chapter uses an ecological perspective to explore individual, social, and environmental-level risk and protective factors related to adolescent sexual and reproductive health behaviors and outcomes. Implications include strategies to promote sexual and reproductive health that address individual behaviors, as well as the social and environmental context in which adolescents live.