Background: This process study is a companion to a randomized evaluation of a school-based, peer-led comprehensive sexual health education program, Teen Prevention Education Program (Teen PEP), in which 11th- and 12th-grade students are trained by school health educators to conduct informative workshops with ninth-grade peers in schools in North Carolina. The process study was designed to understand youth participants' perspectives on the program in order to gain insight into program effectiveness. Methods: This is a mixed-methods study in 7 schools, with online surveys (N = 88) and 8 focus groups with peer educators (N = 116), end-of-program surveys (N = 1122), 8 focus groups with ninth-grade workshop participants (N = 89), and observations of the Teen PEP class and workshops during the semester of implementation in each school, 2012-2014. Results: Both peer educators and ninth graders perceived benefits of participating in Teen PEP across a range of domains, including intentions, skills, and knowledge and that the peer education modality was important in their valuation of the experience. Conclusions: Our findings suggest that the peer-led comprehensive sexual health education approach embodied in Teen PEP can be an important educational mechanism for teaching students information and skills to promote sexual health.