Up to 2016, low- and middle-income countries mostly introduced routine human papillomavirus (HPV) vaccination for just a single age-cohort of girls each year. However, high-income countries have reported large reductions in HPV prevalence following "catch-up" vaccination of multiple age-cohorts in the year of HPV vaccine introduction. We used the mathematical model PRIME to project the incremental impact of vaccinating 10- to 14-year-old girls compared to routine HPV vaccination only in the same year that routine vaccination is expected to be introduced for 9-year-old girls across 73 low- and lower-middle-income countries. Adding multiple age-cohort vaccination could increase the number of cervical cancer deaths averted by vaccine introductions in 2015-2030 by 30-40% or an additional 1.23-1.79 million over the lifetime of the vaccinated cohorts. The number of girls needed to vaccinate to prevent one death is 101 in the most pessimistic scenario, which is only slightly greater than that for routine vaccination of 9-year-old girls (87). These results hold even when assuming that girls who have sexually debuted do not benefit from vaccination. Results suggest that multiple age-cohort vaccination of 9- to 14-year-old girls could accelerate HPV vaccine impact and be cost-effective.