INTRODUCTION: HIV treatment guidelines now recommend antiretroviral therapy (ART) initiation regardless of CD4 count to maximize benefit both for the individual and society. It is unknown whether the initiation of ART at higher CD4 counts would affect adherence levels. We investigated whether initiating ART at higher CD4 counts was associated with sub-optimal adherence (<95%) during the first 12 months of ART. METHODS: A prospective cohort study nested within a two-arm cluster-randomized trial of universal test and treat was implemented from March 2012 to June 2016 to measure the impact of ART on HIV incidence in rural KwaZulu-Natal. ART was initiated regardless of CD4 count in the intervention arm and according to national guidelines in the control arm. ART adherence was measured monthly using a visual analogue scale (VAS) and pill counts (PC). HIV viral load was measured at ART initiation, three and six months, and six-monthly thereafter. We pooled data from participants in both arms and used random-effects logistic regression models to examine the association between CD4 count at ART initiation and sub-optimal adherence, and assessed if adherence levels were associated with virological suppression. RESULTS: Among 900 individuals who initiated ART ≥12 months before study end, median (IQR) CD4 at ART initiation was 350 cells/mm3 (234, 503); median age was 34.6 years (IQR 27.4 to 46.4) and 71.7% were female. Adherence was sub-optimal in 14.7% of visits as measured by VAS and 20.7% by PC. In both the crude analyses and after adjusting for potential confounders, adherence was not significantly associated with CD4 count at ART initiation (adjusted OR for linear trend in sub-optimal adherence with every 100 cells/mm3 increase in CD4 count: 1.00, 95% CI 0.95 to 1.05, for VAS, and 1.03, 95% CI 0.99 to 1.07, for PC). Virological suppression at 12 months was 97%. Optimal adherence by both measures was significantly associated with virological suppression (p < 0.001 for VAS; p = 0.006 for PC). CONCLUSIONS: We found no evidence that higher CD4 counts at ART initiation were associated with sub-optimal ART adherence in the first 12 months. Our findings should alleviate concerns about adherence in individuals initiating ART at higher CD4 counts, however long-term outcomes are needed. ClinicalTrials.gov NCT01509508.