Retention in HIV care remains a national challenge. Addressing structural barriers to care may improve retention. We examined the association between physician reimbursement and retention in HIV care, including racial differences. We integrated person-level administrative claims (Medicaid Analytic eXtract, 2008-2012), state Medicaid-to-Medicare physician fee ratios (Urban Institute, 2008, 2012), and county characteristics for 15 Southern states plus District of Columbia. The fee ratio is a standardized measure of physician reimbursement capturing Medicaid relative to Medicare physician reimbursement across states. Generalized estimating equations assessed the association between the fee ratio and retention (≥2 care markers ≥90 days apart in a calendar year). Stratified analyses assessed racial differences. We varied definitions of retention, subsamples, and definitions of the fee ratio, including the fee ratio at parity. The sample included 55,237 adult Medicaid enrollees with HIV (179,002 enrollee years). Enrollees were retained in HIV care for 76.6% of their enrollment years, with retention lower among non-Hispanic Black (76.1%) versus non-Hispanic White enrollees (81.3%, P < 0.001). A 10-percentage point increase in physician reimbursement was associated with 4% increased odds of retention (adjusted odds ratio 1.04, 95% confidence interval: 1.01 to 1.07). In stratified analyses, the positive, significant association occurred among non-Hispanic Black (1.08, 1.05-1.12) but not non-Hispanic White enrollees (0.87, 0.74-1.02). Findings were robust across sensitivity analyses. When the fee ratio reached parity, predicted retention increased significantly overall and for non-Hispanic Black enrollees. Higher physician reimbursement may improve retention in HIV care, particularly among non-Hispanic Black individuals, and could be a mechanism to promote health equity.