BackgroundTo reduce HIV/AIDS related mortality of children, adherence to antiretroviral treatment (ART) is critical in the treatment of HIV positive children. However, little is known about the association between ART adherence and different orphan status. The aims of this study were to assess the ART adherence and identify whether different orphan status was associated with the child’s adherence.MethodsA total of 717 HIV positive children and the same number of caregivers participated in this cross-sectional study. Children’s adherence rate was measured using a pill count method and those who took 85% or more of the prescribed doses were defined as adherent. To collect data about adherence related factors, we also interviewed caregivers using a structured questionnaire.ResultsOf all children (N = 717), participants from each orphan category (double orphan, maternal orphan, paternal orphan, non-orphan) were 346, 89, 169, and 113, respectively. ART non-adherence rate of each orphan category was 59.3%, 44.9%, 46.7%, and 49.7%, respectively. The multivariate analysis indicated that maternal orphans (AOR 0.31, 95% CI 0.12–0.80), paternal orphans (AOR 0.35, 95% CI 0.14–0.89), and non-orphans (AOR 0.45, 95% CI 0.21–0.99) were less likely to be non-adherent compared to double orphans. Double orphans who had a sibling as a caregiver were more likely to be non-adherent. The first mean CD4 count prior to initiating treatment was 520, 601, 599, and 844 (cells/ml), respectively (p<0.001). Their mean age at sero-status detection was 5.9, 5.3, 4.8, and 3.9 (year old), respectively (p<0.001).ConclusionsDouble orphans were at highest risk of ART non-adherence and especially those who had a sibling as a caregiver had high risk. They were also in danger of initiating ART at an older age and at a later stage of HIV/AIDS compared with other orphan categories. Double orphans need more attention to the promote child’s adherence to ART.