In Sierra Leone, HPV vaccination coverage fell sharply from over 100% in 2022 to 31.3% in 2023, prompting CHAI and the Ministry of Health EPI programme to conduct formative research across the four lowest-performing districts — Bonthe, Koinadugu, Kenema, and Western Area Rural. A mixed-methods study combining facility data audits and semi-structured interviews with healthcare workers, teachers, and caregivers found that barriers stemmed not from outright refusal but from knowledge gaps, sociocultural influences including infertility myths, weak coordination between health facilities and schools, inconsistent use of HPV vaccination registers, and logistical challenges in reaching out-of-school girls and remote communities. Healthcare workers additionally identified gaps in their capacity to address hesitancy and communicate the single-dose schedule, alongside resistance from male household decision-makers. The findings point to targeted refresher training for health workers and teachers, culturally adapted community engagement, strengthened data management, and enhanced outreach as essential levers for coverage recovery.