BACKGROUND: Age-specific retention challenges make antiretroviral therapy (ART) initiation in adolescents difficult, often requiring a lengthy preparation process. This needs to be balanced against the benefits of starting treatment quickly. The optimal time to initiation duration in adolescents is currently unknown. OBJECTIVE: To assess the effect of time to ART initiation on mortality and loss to follow-up (LTFU) among treatment eligible adolescents. METHODS: We conducted a retrospective cohort analysis among 1499 ART eligible adolescents aged ≥10 to <19 years registered in a public sector HIV program in Bulawayo, Zimbabwe, between 2004 and 2011. Hazard ratios (HR) for mortality and LTFU were calculated for different time to ART durations using multivariate Cox regression models. RESULTS: Median follow-up duration was 1.6 years. Mortality HRs of patients who initiated at 0 to ≤7 days, >14 days to ≤1 month, >1 to ≤2 months, >2 months, and before initiation were 1.59, 1.19, 1.56, 1.08, and 0.94, respectively, compared with the reference group of >7 to ≤14 days. LTFU HRs were 1.02, 1.07, 0.85, 0.97, and 3.96, respectively. Among patients not on ART, 88% of deaths and 85% of LTFU occurred during the first 3 months after becoming ART eligible, but only 37% and 29% among adolescents on ART, respectively. CONCLUSIONS: Neither mortality or LTFU was associated with varying time to ART. The initiation process can be tailored to the adolescents' needs and individual life situations without risking to increase poor treatment outcomes. Early mortality was high despite rapid ART initiation, calling for earlier rather than faster initiation through HIV testing scale-up.