Donors, practitioners and scholars are increasingly interested in harnessing the potential of social norms theory to improve adolescents' sexual and reproductive health outcomes. However, social norms theory is multifaceted, and its application in field interventions is complex. An introduction to social norms that will be beneficial for those who intend to integrate a social norms perspective in their work to improve adolescents' sexual health in Africa is presented. First three main schools of thought on social norms, looking at the theoretical standpoint of each, are discussed. Next, the difference between two important types of social norms (descriptive and injunctive) is explained and then the concept of a -reference group‖ is examined. The difference between social and gender norms are then considered, highlighting how this difference is motivated by existing yet contrasting approaches to norms (in social psychology and gender theory). In the last section, existing evidence on the role that social norms play in influencing adolescents' sexual and reproductive health are reviewed. Conclusions call for further research and action to understand how norms affecting adolescents' sexual and reproductive health and rights (SRHR) can be changed in sub-Saharan Africa.