OBJECTIVE: The study aimed to investigate the impact of COVID-19 on the cascade of HIV care for people living with HIV (PLHIV) in Ethiopia. DESIGN: A retrospective longitudinal study. SETTING: The study was conducted in North Showa Zone, Ethiopia, from pre-COVID-19 (January 2018-December 2019) and during COVID-19 (January 2020-December 2021). PARTICIPANTS: We identified 61901 records from 3925 PLHIV, of which 23 848 were recorded during the pandemic. MAIN OUTCOME MEASURE: We investigated indicators from four stages of the HIV care cascade, including HIV screening and diagnosis, HIV care, HIV treatment and HIV disease progression, according to a WHO framework. The indicator changes were assessed with incidence rate ratios (IRRs). RESULTS: For HIV screening and diagnosis, the monthly number of HIV tests experienced a 46% decline from 2520 to 1361 since the pandemic (IRR 0.553; 95% CI 0.546 to 0.561). For HIV care, the monthly number of consultations was reduced by 49.6% (from 1582 to 798) since the pandemic (IRR 0.591; 95% CI 0.581 to 0.601). Similarly, the monthly number of viral load tests was reduced by 42.8% (IRR 0.614; 95% CI 0.581 to 0.650). For HIV treatment, the number of antiretroviral therapy (ART) initiations was reduced by 27.8% and the number of ART adherence by 52.5% since the pandemic. For HIV disease progression, the monthly number of PLHIV achieving viral suppression was reduced by 61.6%, while HIV-related deaths doubled during the pandemic. CONCLUSION: The study highlights pandemic-induced disruptions in the cascade of care for PLHIV. Targeted interventions are necessary to protect PLHIV in public health emergencies.