<p>Young people living with HIV (YLWH) have some of the lowest rates of retention in HIV care, putting them at risk for negative health outcomes. To better understand retention in care in this age group, we conducted a retrospective cohort analysis of YLWH initiating care at a multidisciplinary, adolescent-focused HIV clinic (N = 344). Retention was calculated using a variety of definitions, and relationships between different definitions were assessed. During the 1-year study period, on average YLWH missed two scheduled appointments, and attended 80% of appointments, usually at least once every 3&nbsp;months. About one-quarter experienced a 6-month gap in care and about two-thirds met the Health Resources and Services Administration's retention criteria. Although most retention definitions were significantly correlated, not all were. Researchers, clinicians, and policymakers should consider the impact of varying definitions of retention, in order to optimally measure this outcome in YLWH, a key vulnerable population.</p>