BACKGROUND: The coronavirus disease 2019 (COVID-19) pandemic poses challenges to paediatric and adolescent HIV treatment programme. Modelling exercises raised concerns over potential impact of disruptions. OBJECTIVES: To describe the impact of the COVID-19 pandemic on viral load (VL) testing among infants, children and adolescents on antiretroviral treatment (ART) in Durban, South Africa. METHOD: Routinely collected, aggregated data of monthly VL counts done on all those less than 19 years old from January 2018 to January 2022 was analysed. An interrupted time series analysis using a Prais-Winsten linear regression model, including terms for lockdowns and excess mortality determined VL trends. RESULTS: The unadjusted mean VL was 2166 (confidence interval [CI]: 252.2) and 2016 (CI: 241.9), P = 0.039, and percentage VL suppression rates (72.9%, CI: 2.4% vs 73.6%, CI: 1.8%) across COVID and pre-COVID periods, showing no significant difference, P = 0.262. In the interrupted time series analysis, modelled monthly VL counts did not differ significantly by lockdown level (e.g., level 5 lockdown: -210.5 VLs, 95% CI: -483.0 to +62.1, P = 0.138) or excess mortality (-0.1, 95% CI: -6.3 to 6.1, P = 0.969). A significant downward trend in VL testing over time, including during the pre-COVID-19 period (-6.6 VL per month, 95% CI: -10.4 to -2.7, P = 0.002), was identified. CONCLUSION: Viral load suppression for children and adolescents were not negatively affected by COVID-19. A trend of decrease in VL testing predated COVID-19. WHAT THIS STUDY ADDS: Evidence presented that HIV VL testing and suppression rates in children and adolescents in a high burden setting were sustained through the COVID pandemic.