Adolescents living with HIV (ALHIV) in sub-Saharan Africa (SSA) face multiple challenges which exacerbate their risks for treatment failure and poor psychosocial outcomes. Peer support interventions can be a mechanism to potentially improve their health outcomes. The purpose of this dissertation was to use innovative approaches to design and evaluate peer support interventions for ALHIV in sub-Saharan Africa, which were explored in three ways. First, an integrated review was conducted to understand the state of the science regarding the efficacy of peer support interventions in improving psychosocial and treatment outcomes among ALHIV in SSA. Second, a hybrid inductive-deductive thematic approach was used to identify implementation determinants regarding the peer delivery of a brief psychological intervention (i.e., Friendship Bench) among ALHIV in Gaborone, Botswana. Our findings provide eight implementation determinants (i.e., six barriers and two facilitators) to consider in future adaptations of Friendship Bench for ALHIV. The six barriers identified were client accessibility, parent disapproval, lack of financial resources, counselor psychological wellbeing, client reticence and confidentiality concerns, and scheduling procedures. The two facilitators were counselors’ perceived value of the intervention and peer delivery of counseling. Third, a behavioral economics design approach (i.e., NUDGE) was used to identify behavioral barriers to antiretroviral therapy adherence among ALHIV in Eswatini, and subsequently design intervention prototypes that peer lay health workers (i.e., expert clients) can use to address these barriers. The following barriers were identified and validated by expert clients: fear of public and interpersonal disclosure of HIV status, anger and lack of acceptance related to delayed HIV disclosure among parents, refusal to receive adherence instructions from adults, and psychological barriers related to food insecurity. Lastly, prototype ideas to address these barriers were developed and vetted by expert clients. Overall, expert clients favored four prototype ideas that they believed were feasible to implement at a low cost: commitment contracts, message framing, group regret lotteries, and messenger type interventions. The overall findings and insights from this dissertation provide the preliminary steps for future work utilizing behavioral economics and implementation science to optimize peer support interventions for ALHIV in SSA.