HIV remains a disease of public health importance, with an estimated 39.0 million people living with the virus globally as of 2022. The Association for Reproductive and Family Health (ARFH) is implementing the Integrated Child Health and Social Services Award (ICHSSA-2) project in Lagos with support from USAID. Triggers of unsuppressed viral load were examined among HIV-infected children and adolescents enrolled in the project. A descriptive cross-sectional analysis of routine data was conducted among 207 children and adolescents living with HIV (C/ALHIV) aged 1 to 17 years, enrolled in USAID-supported healthcare facilities across eleven (11) Local Government Areas (LGAs) in Lagos State. The data were analyzed using descriptive statistics, and the significance of the association was determined using the Chi-square test. Slightly above one-third (36.7%) of the C/ALHIV enrolled were between the ages of 14 and 17 years, while only 8.7% were within the age group of 1 to 4 years. The highest proportion of C/ALHIV (24.2%) was from Ajeromi LGA. Missed pills accounted for more than half (51.7%) of the reasons identified for unsuppressed viral load among clients, followed by a busy schedule (15.4%), forgetfulness, and missed appointments (8.2%), respectively. More than half (51.4%) of the clients who reported missed pills were males. The identified triggers of sub-optimal HIV viral load and corresponding LGAs were found to be statistically significant (p < 0.05). Incorporating these identified triggers as part of routine adherence counseling for clients during clinic and home visits will undoubtedly contribute to and accelerate progress towards achieving the UNAIDS 3rd 95 goal.