Background: Human immunodeficiency virus is the public health issue that affects the health of an individual through reducing body’s immune system. Despite, antiretroviral therapy could reduce the transmission of human immunodeficiency virus and related morbidity, loss to follow up is a main challenge among human immunodeficiency virus infected children. Objective:The aim of this study was to assess the incidence and predictors of loss to follow up among under 15 years old children on highly active antiretroviral therapy at Dessie referral hospital, North east Ethiopia, 2020.