This study began by exploring the factors that influence the sexual health information sources available to Ugandan adolescents and how they decide what sources to use. Guided by participatory action research, focus group discussions and interviews were conducted with students and teachers from two secondary schools in western Uganda. In addition to external barriers, the young people had a complex internal process that they applied when choosing sources. Using these findings, the participants collaborated to develop and initiate a school-based peer education program to prevent unwanted sexual health outcomes (HIV, pregnancy, sexually transmitted infections). The peer educators received participatory training on sexual health topics. Through their involvement in the project, peer educators felt prepared and confident to be peer educators and had already had opportunities to provide advice to their peers. The students continued the peer education program; it expanded to other schools where successes were also achieved.