Despite global efforts to improve vaccination coverage, the number of zero-dose and under-immunized children has increased in Africa, particularly in Nigeria, which has over 2.1 million unvaccinated (zero-dose) children, the highest in the continent. This scoping review systematically maps and summarizes existing literature on the barriers and facilitators of immunization in Nigeria, focusing on regional inequalities. A comprehensive search of electronic databases was conducted, encompassing all data from their inception to October 2023, to identify articles on the determinants of routine immunization uptake in Nigeria. Eligible studies were evaluated using predefined criteria, and the data were analyzed and visualized. Findings underscore the need for region-specific interventions that address these unique barriers to improve immunization coverage across Nigeria. Tailored approaches that consider the socio-economic, cultural, and logistical challenges specific to each region are essential to bridge the immunization gap.