In Ethiopia, a retrospective microcosting study of the late 2024 HPV vaccine multi-age cohort (MAC) campaign — targeting girls aged 9–14 across 82 health facilities in four regions — estimated the financial cost of delivering a single dose at US$0.66 and the economic cost at US$1.67 per fully vaccinated girl, excluding vaccine and immunization supply costs. School-based sessions were the predominant delivery strategy (90% of facilities), supplemented by community outreach (73%). Compared to the two-dose single-age cohort regimen delivered between 2019 and 2021, the single-dose MAC approach yielded an 88% reduction in financial costs and a 91% reduction in economic costs per fully vaccinated girl. The findings provide real-world evidence that switching to single-dose vaccination of multi-age cohorts can substantially reduce program costs and strengthen long-term sustainability.