With the rise of technology-based interventions for HIV risk reduction among adolescents, research is needed to assess how youth participate in these strategies. We used qualitative content analysis to examine youth's posts in an online peer support intervention through the Adolescent Trials Network (ClinicalTrials.gov NCT03134833, registered May 1, 2017) for youth at higher risk of or living with HIV. We analyzed 308 posts across 85 conversations related to sexual health from 144 peer support participants. Conversation topics included risk reduction, partner navigation, sexual activity, awareness/advocacy, and consent/harassment. Results may inform the design, adaptation, and implementation of digital peer support interventions.