This study examined associations between scores on the Adolescent Medication Barriers Scale (AMBS) and the Parent Medication Barriers Scale (PMBS), patient and family factors, and medication adherence outcomes. Patients and caregivers from a pediatric solid organ transplantation (SOT) program were recruited for participation. Pediatric SOT recipients ages 10 to 21 years were eligible for participation. Analyses included reliability analyses and regression modeling with posttransplant medication adherence measured by Medication Level Variability Index scores. Seventy-three patients and caregivers completed an AMBS or PMBS questionnaire. Patient–caregiver inter-rater reliability was poor to fair. Greater medication barriers were reported among younger and female patients and families with more children. AMBS scores predicted greater nonadherence, while the PMBS was not predictive of adherence. Results point to the difficulty of assessing barriers to medication adherence and the lack of agreement between adolescent patients and caregivers. AMBS scores were more closely aligned with medication nonadherence, whereas PMBS scores may have been more influenced by family social factors. Adolescent reports of medication barriers may offer multidisciplinary transplant teams greater clinical utility when addressing these challenges with patients. Transplant social workers and psychologists should engage adolescents and caregivers in efforts to address medication nonadherence.