Multimonth dispensing (MMD) enables less frequent clinic visits and improved outcomes for people living with HIV, but few children and adolescents living with HIV (CALHIV) are on MMD. At the end of the October-December 2019 quarter, only 23% of CALHIV receiving antiretroviral therapy (ART) through SIDHAS project sites in Akwa Ibom and Cross River states, Nigeria, were receiving MMD. In March 2020, during COVID-19, the government expanded MMD eligibility to include children and recommended rapid implementation to minimize clinic visits. SIDHAS provided technical assistance to 36 "high-volume" facilities-≥5 CALHIV on treatment-in Akwa Ibom and Cross River to increase MMD and viral load suppression (VLS) among CALHIV, toward PEPFAR's 80% benchmark for people currently on ART. We present change in MMD, viral load (VL) testing coverage, VLS, optimized regimen coverage, and community-based ART group enrollment among CALHIV from the October-December 2019 quarter (baseline) to January-March 2021 (endline) based on retrospective analysis of routinely collected program data. We compared MMD coverage (primary objective), and optimized regimen coverage, community-based ART group enrollment, VL testing coverage, and VLS (secondary objectives), among CALHIV 18 years and younger pre-/post-intervention (baseline/endline) at the 36 facilities. We excluded children younger than two years, who are not recommended for or routinely offered MMD. The extracted data included age, sex, ART regimen, months of ART dispensed at last refill, most recent VL test results, and community ART group enrollment. Data on MMD-three or more months of ARVs dispensed at one time-were disaggregated into three to five months (3-5-MMD) vs. six or more months (6-MMD). VLS was defined as ≤1,000 copies. We documented MMD coverage by site, optimized regimen, and VL testing and suppression. Using descriptive statistics, we summarized the characteristics of CALHIV on MMD and non-MMD, number of CALHIV on optimized regimens, and proportion enrolled in differentiated service delivery models and community-based ART refill groups. For the intervention, SIDHAS technical assistance was data driven: weekly data analysis/review, site-prioritization scoring, provider mentoring, line listing eligible CALHIV, pediatric regimen calculator, child-optimized regimen transitioning, and community ART models. The proportion of CALHIV ages 2-18 receiving MMD increased from 23% (620/2,647; baseline) to 88% (3,992/4,541; endline), while the proportion of sites reporting suboptimal MMD coverage among CALHIV (<80%) decreased (100% to 28%). In March 2021, 49% of CALHIV were receiving 3-5-MMD and 39% 6-MMD. In October-December 2019, 17%-28% of CALHIV were receiving MMD; by January-March 2021, 99% of those 15-18 years, 94% 10-14 years, 79% 5-9 years, and 71% 2-4 years were on MMD. VL testing coverage remained high (90%), while VLS increased (64% to 92%). The proportion on pediatric-optimized regimens increased (58% to 79%). MMD was feasible among CALHIV without compromising VLS. Expanded eligibility criteria, line listing eligible children, monitoring pediatric antiretroviral stock, and data use contributed to positive results. Future efforts should address low 6-MMD uptake related to stock limitations and synchronize antiretroviral refill pickup with VL sample collection.