This study examined the influence of Primary Health Care (PHC) financing mechanisms on out-of-pocket healthcare expenditures among service users in Kogi State, Nigeria, with a view to assessing their implications for achieving Universal Health Coverage (UHC). The study adopted a descriptive cross-sectional survey design. The target population comprised 1,344,493 residents and users of PHC facilities across six selected Local Government Areas. Using Taro Yamane's formula, a sample size of 400 respondents was determined and proportionately distributed across the selected LGAs. A multi-stage sampling technique was employed to select respondents, while 20 key informants were purposively selected for interviews. Primary data were collected through structured questionnaires and semi-structured interview, while secondary data were obtained from relevant textbooks, journal articles, government publications, and policy documents. Of the 400 questionnaires administered, 372 were completed and returned. Quantitative data were analyzed using descriptive statistics and Simple Linear Regression with the aid of IBM SPSS Statistics Version 25, while qualitative data were analyzed using thematic content analysis. The findings revealed that most respondents perceived PHC services as unaffordable and reported that financial barriers significantly limited their utilization of PHC services. Respondents also identified inadequate availability of essential medicines as a major challenge confronting PHC facilities. Regression analysis showed that PHC financing mechanisms have a statistically significant influence on out-of-pocket healthcare expenditures among service users in Kogi State. Findings from the key informant interviews further revealed that inadequate budgetary allocation, delayed release of funds, limited health insurance coverage, frequent stock-outs of essential medicines, and weak implementation of financing programmes continue to undermine financial risk protection and the attainment of Universal Health Coverage. The study recommended increased government funding for PHC, timely disbursement of the Basic Health Care Provision Fund, expansion of health insurance coverage, regular supply of essential medicines, strengthening of PHC governance and accountability systems, and intensified monitoring and evaluation to accelerate progress toward Universal Health Coverage.