BackgroundWe aimed to determine antiretroviral therapy (ART) initiation timing and outcomes in people living with HIV (PLHIV) receiving tuberculosis treatment in KwaZulu-Natal, South Africa.MethodsWe performed a retrospective cohort analysis of routinely collected de-identified data from 62 clinics including PLHIV not already receiving ART aged ≥16 years, starting tuberculosis treatment between October 2016-November 2019. Multivariable Poisson regression models with robust standard errors evaluated associations between timing of ART initiation (after starting tuberculosis treatment) and successful tuberculosis treatment, and 6-month HIV viral load (VL) < 50 copies/mL.ResultsAmong 5,548 PLHIV with tuberculosis, 29.8% initiated ART within 15 days ("early"), 36.2% in 16-56 days, 8.7% in 57-210 days, with 25.3% not initiating ART by 7 months. Proportions with successful tuberculosis treatment were similar comparing 16-56 and 57-210 days to early initiation, with a lower likelihood of successful tuberculosis outcome with no ART within 7 months (adjusted risk ratio [aRR] 0.81 [0.77-0.86], p < 0.001). In those with a known VL 6 months post-ART initiation (n = 2,658), initiation within 57-210 days had a lower likelihood of viral suppression (aRR 0.90 [0.82-0.99], p < 0.03).ConclusionAlthough <30% of PLHIV with tuberculosis initiated ART early, this was associated with better tuberculosis outcomes and VL suppression.