Antiretroviral therapy (ART) use in long-term care (LTC) is lower than expected making it critical that facilitators/barriers are identified. A convergent mixed-methods design, sought convergent, complementary, and contradicting factors related to ART adherence in LTC. Two identical quantitative analyses assessed the change in the proportion of days covered (PDC) by ART before and after transitioning to LTC in Medicare (LTC stays for people with HIV (PWH) in [1] 2017-2019 Medicare Advantage [MA]; [2] a 5% random 2014-2019 Traditional Medicare [TM] sample). Linear regression predicting change controlled for person-level and facility-level characteristics. Qualitative interviews from residents (n=11) and providers (n=6) of a HIV-specialized LTC facility focused on barriers/facilitators to ART adherence in LTC. Demographics of PWH were similar across qualitative and quantitative studies with mean age 60-61 years old, >50% were non-White. Convergent: Dual eligibility and Black race were associated with ART use. For-profit status was associated with not being on ART. The facility was not-for-profit, most participants were non-white, on Medicaid, all were ART adherent. Complementary: The facility ensured frequent patient-provider interactions, routine screening at admission, viral load monitoring, and a collaborative approach to care. Contradictory: Polypharmacy was associated with lower PDC. Interviews identified specific strategies to mitigate polypharmacy and optimize ART adherence, through team-oriented medication reconciliation. Quantitatively, PWH in MA and TM using LTC were similar and found more person-level facilitators of ART adherence, while qualitative findings showed environmental factors not found in claims data make a difference in ART adherence.