Between December 2014 and September 2016, we conducted a prospective cohort study in eight health facilities in Ethiopia. Eligibility criteria included age 3 months-14 years; being on ART for not more than a month. Of 309 children, 304 were included, 52% were male. During 287.7 person-years of observation (PYO), 24 attritions were recorded, yielding an attrition rate of 8.3 per 100 PYO. Younger children, those from rural areas, and children with anaemia were at higher risk of attrition, especially during the early months of treatment, and therefore should be prioritized during treatment follow-up.