Adolescence is an important developmental stage usually characterized by physical changes, psychosocial changes, and a tendency towards new experiences, such as sexual activity. It is generally understood that adolescents learn about sexual and reproductive health from multiple sources, including parents, friends, and the media. Less studied - particularly in non-Western and/or African contexts - is the role of siblings in shaping adolescents' knowledge, attitudes, and behaviors. This study is a secondary analysis of data collected from focus group discussions (FGDs), in-depth interviews (IDIs), and a nationally representative survey among 12-19 year-olds in Ghana as part of a four-country project assessing the sexual and reproductive health of adolescents in sub-Saharan Africa. Through a mixed methods approach, the present study examines similarities and differences in the health information that adolescents receive from various sources. Using social learning theory and differentiation theory as frameworks, the study hones in on the contributions of siblings. Analyses of all three data sources produce complementary results. FGDs and IDIs show clear similarities in the timing and nature of sexual and reproductive health information that adolescents receive from other sources and from siblings, especially regarding sexual abstinence and preventing early pregnancy. The FGDs and IDIs also provide evidence of social and observational learning, showing that siblings serve as agents of socialization, advisors, confidants, and role models. Findings from the survey and IDIs highlight the preponderance of communication and interactions between same-gender sibling dyads. Additionally, multivariate analyses show that older adolescents (15-19 years) are twice as likely to communicate with a sibling about sex-related matters as younger ones and that the likelihood is even higher among male adolescents who have at least one older sibling. Adolescents from rural areas, however, were significantly less likely to communicate with a sibling. Besides establishing the need to consider siblings as an important target group in adolescent and family-centered policy and programmatic interventions in Ghana, results from this study emphasize the duality of adolescents as siblings who exchange sexual and reproductive health information and who can potentially impact the transition to adulthood.