OBJECTIVES: Nigeria like other developing countries adopts routine immunization as a strategy to reduce the burden of preventable diseases but evidence suggests that coverage is inadequate. Adequate healthcare funding can improve the supply of vaccines, as well as ensure effective and efficient administration. The study aimed at exploring the impact of health sector funding on immunization services in Abuja (FCT), Nigeria. METHODS: Following ethics approval from the National Assembly Management, a mixed methods approach underpinned data collection and analysis in the study. Secondary data from six FCT area councils, from 2010 to 2012 were reviewed using documentary analysis. Additionally, a piloted and validated cross sectional survey was designed to collect the data from 650 randomly selected members of the public between December 2014 and March 2015. Data collected included demographic details and responses on issues pertaining to immunization and access to healthcare. Descriptive and inferential statistics were applied using SPSS. RESULTS: Analysis revealed that a 28% reduction in budgetary allocation from N18,592,631,805 in 2010 to N13,363,515,169 in 2012 led to a decline in immunization uptake in the FCT, from 89.4% coverage in 2010 to 79.9% in 2012. The survey revealed that only about half of the sample had taken steps to ensure that their children were immunized (51.9%). Almost a third (30.6%) indicated that they had to pay for routine immunization, and amongst those who had vaccinated their children, the majority (74.6%) preferred services from public hospitals (p<0.05). CONCLUSIONS: Due to the mixed methods approach employed, a relationship between health system funding and immunization coverage has emerged. Out of pocket payment for immunization is a significant barrier to access, particularly in poor populations. The confidence in public hospitals shown in this study can be leveraged to increase access to vaccines if the relevant capacity is provided.