Human papillomavirus (HPV) vaccine uptake among adolescent girls is critical to reducing the burden of HPV-related cancers in Nigeria. This study assesses the factors influencing caregivers' acceptance of HPV vaccination for their charges, using the Fogg Behavior Model (FBM) as a theoretical framework. We analyzed cross-sectional data from 1429 caregivers of girls aged 9-17 in six Nigerian states, using a survey instrument based on the FBM. Participants were recruited via Facebook and Instagram advertisements and interviewed through Facebook Messenger in August and September 2023. The study received ethical clearance from Nigeria's National Health Research Ethics Committee. We applied bivariate and multivariate analyses to assess the relationships between the caregiver's perception of how likely their adolescent girl was to get vaccinated in the next 12 months and motivation, ability, social factors (such as discussions with family and friends), injunctive norms, previous COVID-19 vaccination, and respondents' sociodemographic characteristics. Adjusted odds ratios derived from logistic regression analyses revealed that caregivers' motivation and ability, as well as social factors, were significantly associated with their perception that the adolescent girl in their care would get vaccinated within the next 12 months. Our findings suggest that behavioral interventions tailored to enhance motivation, ability, and social support among caregivers could significantly increase HPV vaccine uptake among adolescent girls in Nigeria.