Background: Despite encouraging results from clinical trials and in highincome countries, large-scale data on the effectiveness and safety of dolutegravir (DTG) in children and adolescents living with HIV (CALHIV) are lacking in low-and middle-income countries (LMICs). Methods: Retrospective analysis was performed among CALHIV 0-19 years old and weighing greater than or equal to 20 kg who received DTG from 2017 to 2020 at sites in Botswana, Eswatini, Lesotho, Malawi, Tanzania and Uganda to determine effectiveness, safety and predictors of viral load suppression (VLS) among CALHIV using DTG, including through single drug substitutions (SDS). Results: Among 9419 CALHIV using DTG, 7898 had a documented post-DTG VL, and VLS post-DTG was 93.4% (7378/7898). VLS for antiret-roviral therapy (ART) initiations was 92.4% (246/263), and VLS was maintained for the ART-experienced [92.9% (7026/7560) pre-vs. 93.5% (7071/7560) post-DTG; P = 0.14). Among previously unsuppressed, 79.8% (426/534) achieved VLS with DTG. Only 5 patients reported a Grade 3 or 4 adverse event (0.057 per 100 patient-years) requiring DTG discontinuation. History of protease inhibitor-based ART [odds ratio (OR) = 1.53; 95% confidence interval (CI): 1.16-2.03], care in Tanzania (OR = 5.45; 95% CI: 3.41-8.70), and being 15-19 years old (OR = 1.31; 95% CI: 1.03-1.65) were associated with gain of VLS post-DTG. Predictors of VLS on DTG included VLS before DTG (OR = 3.87; 95% CI: 3.03-4.95) and using the once-daily, single tab tenofovir-lamivudine-DTG regimen (OR = 1.78; 95% CI: 1.43-2.22). SDS maintained VLS [95.9% (2032/2120) pre-vs. 95.0% (2014/2120) post-SDS with DTG; P = 0.19], and 83.0% (73/88) of unsuppressed gained VLS using SDS with DTG. Conclusions: We found DTG to be highly effective and safe within our cohort of CALHIV in LMICs. These findings can empower clinicians to prescribe DTG confidently to eligible CALHIV.