OBJECTIVE: Oral pre-exposure prophylaxis (PrEP) is an important HIV prevention method and studies have shown that young people ages 15-24 have difficulty adhering to daily PrEP. The field of PrEP delivery for young people is relatively nascent and lessons about potential PrEP adherence interventions could be learned from the larger evidence base of adherence interventions for other daily medications among youth. DESIGN: Systematic review of adherence support interventions for adolescents. METHODS: We searched PubMed, CINAHL, EMBASE, and PsycINFO through January 2020 for oral contraceptive pill (OCP), antiretroviral therapy (ART), asthma, and diabetes medication adherence interventions. We reviewed primary articles about OCP adherence interventions and reviewed systematic reviews for ART, asthma, and diabetes medication adherence interventions. Studies were retained if they included participants' ages 10-24 years; measured OCP, ART, asthma, or diabetes medication adherence; and were systematic reviews, randomized trials, or quasi-experimental studies. RESULTS: Fifteen OCP articles and 26 ART, diabetes, and asthma systematic reviews were included. Interventions that improved medication adherence for OCPs, ART, asthma, and diabetes treatment included reminder text messages, computer-based and phone-based support, and enhanced counseling. Multi-month prescriptions and same-day pill starts also were found to improve OCP adherence and continuation. Adolescent-friendly clinics and peer-based counseling significantly improved ART adherence, and telemedicine interventions improved diabetes medication adherence. CONCLUSION: Interventions that improve medication adherence among youth include enhanced counseling, extended pill supply, adolescent-friendly services, and text message reminders. PrEP programs could incorporate and evaluate such interventions for their impact on PrEP adherence and continuation among at-risk adolescents.