Viral suppression assesses the success of HIV/AIDS treatment and can avert or reduce transmission of infection. Several factors contribute to viral suppression and may vary in different settings and age groups, hence the need to study the associated factors in different populations. The aim of the research was to study the level of viral suppression and its predictors among adolescents living with HIV (ALHIV), who knew their status, at the paediatric infectious diseases unit of a tertiary hospital in Nigeria. This was a descriptive cross-sectional study of 50 consecutive ALHIV who had full disclosure of their HIV diagnosis. There were 29 females with a female to male ratio of 1.38:1. Age range was 10 to 19 years. Mean age was 15.06 ± 2.26 years. A pretested questionnaire was used together with information retrieved from case notes. Socio-demographic data and responses to possible factors affecting viral suppression were obtained and recorded in a proforma. Viral load ranged from <40 to 522,244 HIV RNA copies/ml of blood. Viral suppression rate was 82.00 with 22.00% in those aged 10 to 14 years and 60.00% in those between 15 and 19 years. Factors significantly associated with viral suppression were: Parents being alive (p=0.035), caregivers being on routine medications (p=0.003), missing medications (p=0.0001), number of missed doses of antiretroviral medications (p=0.001), and the current regimen of antiretroviral therapy (p=0.034). In conclusion, viral suppression is approaching UNAIDS target for 2020 and factors related to good adherence to antiretroviral regimens were significant associations.