BACKGROUND: The goal of antiretroviral therapy (ART) is to achieve a sustained HIV suppressed viral load. However, adolescents often present poor adherence to ART which is associated with lower rates of viral load suppression (VLS). The objective of this study was to determine the viral load suppression levels and the associated factors among adolescents living with HIV (ALHIV) and on ART in Eswatini. METHODS: We conducted cross-sectional analysis of data from 911 adolescents aged 10 to 19 living with HIV and on ART between the period January 2017 and September 2022. We collected data of demographic and clinical variables, using a standardized data abstraction tool. We defined viral load suppression as the latest viral load result of ≤ 1000 copies/ml. Univariable and bivariable logistic regression analysis was done to identify factors associated with VLS and factors with p < 0.1 were included in the multivariable regression analysis to adjust for the confounding effect of other variables such as age, sex, and duration of ART. Factors with p < 0.05 were considered statistically significant. RESULTS: Among the 911 participants, 60% (457) were female. The mean age of the participants was 16.3 years, with mean duration on ART of 1.8 years. Viral suppression was attained by 88.5% (806/911) of the participants. Residence in the Shiselweni region was an independent factor associated with viral load suppression (aOR 0.37; 95% CI 0.15-0.19; p˂0.027). CONCLUSION: Low VLS is a risk factor for increased viral resistance and perpetuates HIV transmission within the population. Achieving viral suppression among ALHIV in Eswatini is challenging as data shows that VLS is way below the UNAIDS 95% cut off level among individuals on ART. This is particularly more problematic in the Shiselweni region, where viral suppression is lower than the other regions. Therefore, reinforcement of public health interventions is needed to improve treatment support for achieving sustained viral suppression among ALHIV in Eswatini.