Antiretroviral pre-exposure prophylaxis (PrEP) holds enormous potential to reduce HIV acquisition in key populations globally. We conducted an exploratory PrEP acceptability study using qualitative methodology among adolescents and service providers in the Western Cape Province of South Africa to inform future PrEP implementation challenges in South Africa and other high-prevalence African countries. Semistructured focus groups and in-depth individual interviews were conducted among 57 adolescents 16-17 years of age, living with and without HIV, and 25 clinical service providers. Adolescents and service providers expressed concerns that the availability of PrEP would lead to sexual disinhibition and a reduction in condom use among adolescents. Unexpected positive impacts included predictions that PrEP might encourage disclosure in serodiscordant partnerships and help normalize pill-taking in the community. Careful age, gender, and developmentally appropriate messaging will be needed to ensure adolescents understand partial efficacy and view PrEP as a component of combination prevention.