We estimated the optimum time to initiate antiretroviral therapy (ART) in a retrospective observational cohort. We observed that ART initiation 7 days or less (n = 817) and 8–30 days (n = 1009) were the most important factors with viral suppression, and had similar viral suppression rate, CD4 T-cell count increase and fractions of individuals with links at least 4 and individuals linked to recent HIV infection in HIV molecular networks. This study provides real-world evidence on the benefits of rapid ART initiation in resource-limited setting.