Black and Hispanic patients who receive care from Black and Hispanic physicians have greater use of preventive care. However, receiving care from racially concordant physicians requires that such physicians are included in private insurance plan networks. Using data from 2019, we examined the extent to which racially concordant physicians are available in the Medicare Advantage (MA) program, which disproportionately enrolls Black and Hispanic Medicare beneficiaries, by linking MA physician networks to physician race and ethnicity to measure the diversity of in-network physicians. On average, 51.1 percent of White physicians in a given beneficiary's county were included in their MA network, compared with 43.2 percent of Black physicians and 44.0 percent of Hispanic physicians. Approximately 20 percent of Black and Hispanic beneficiaries had no available Black or Hispanic physicians included in their MA network, and roughly 41.3 percent and 47.2 percent of counties had no Black or Hispanic physicians, respectively, in any MA network. Our study raises significant concerns about the availability of Black and Hispanic physicians in the MA program.