Hepatitis B virus (HBV) infection remains endemic in Nigeria despite the availability of a safe and effective vaccine, with northern regions bearing a disproportionate burden. In contexts characterised by persistent socio-cultural barriers and low immunisation coverage, understanding the behavioural and structural drivers of vaccine uptake and schedule completion is critical. This study examined the behavioural, normative and contextual determinants of Hepatitis B immunisation uptake and completion in Bauchi Local Government Area (LGA), a high-burden setting in northern Nigeria. A community-based descriptive cross-sectional survey was conducted among 227 adults selected through a multistage sampling technique. Data were collected using a structured questionnaire adapted from validated immunisation tools, capturing indicators of knowledge, perceptions, vaccine confidence, normative influence and structural barriers. Data were analysed using descriptive statistics in IBM SPSS version 26 and interpreted using the WHO Behavioural and Social Drivers (BeSD) Framework and the Theory of Normative Social Behaviour (TNSB). Findings revealed moderate awareness of Hepatitis B (55.5%), but limited detailed knowledge of transmission and vaccination schedules. While perceptions of disease severity were positive, vaccine confidence and peer mobilisation were weak. Normative factors, including male household authority and community influence, significantly shaped decisions, while structural barriers such as limited access and economic constraints hindered completion. The study concludes that vaccination behaviour is driven by the interaction of knowledge gaps, social norms and access barriers. It recommends strengthening health education, engaging community decision-makers and improving service accessibility.