Adherence to antiretroviral therapy (ART) remains one of the greatest obstacles in pediatric HIV care. We sought to determine the prevalence of adherence to ART among undisclosed HIV-infected children and adolescents in Ghana. We analyzed baseline data from HIV-infected children and adolescents aged 7 to 18 years old enrolled in the SANKOFA Pediatric HIV disclosure intervention study in Ghana. Antiretroviral medication adherence was measured using caregiver 3-day recall; child 3-day recall; and pharmacy records for antiretroviral time-to-refill. Four hundred and twenty child-caregiver dyads were enrolled from January 2013 to June 2016. The median adherence (interquartile range), as measured by time-to-refill, was 93.2% (68.0% – 100.0%). However, only 47.5% of children had ≥95% adherence (“good adherence”) using time-to-refill data. Children of caregivers who had received secondary or higher level of education versus no school (aOR, 2.90, 95% Confidence Interval, CI 1.29 to 6.56), p = 0.010) or elementary education only (aOR, 2.20, CI, 1.24 to 3.88, p = 0.007) were more likely to have “good adherence” (≥95%). In this cohort of children unaware of their HIV positive status, median ART adherence rate was sub-optimal (by World Health Organization definition) while 38% had poor adherence (<85%).