Abstract Objectives Despite sustained viral suppression with effective antiretroviral therapy (ART), HIV-infected patients with suboptimal immune recovery are still at high risk of both non-AIDS-related and AIDS-related events. The aim of this study was to investigate determinants potentially associated with suboptimal CD4 + T cell count recovery during free ART with sustained viral suppression among an HIV-infected Yi ethnicity population in Liangshan Prefecture, an area in China with high HIV prevalence. Methods This retrospective study included HIV-infected Yi adults (≥ 18 years and baseline CD4 + T cell count less than 500 cells/μL) for whom ART supported by National Free Antiretroviral Treatment Program was initiated between January 2015 and December 2018 in Zhaojue County, Liangshan Prefecture. Virological suppression (viral load