This study examined accountability, fund utilization and primary healthcare service outcomes under Nigeria’s Basic Health Care Provision Fund (BHCPF) using a health facility-based cross-sectional design involving 276 primary healthcare facilities across the six geopolitical zones. The analysis focused on BHCPF funding received, duration of participation, annual account auditing, functional Ward Development Committee/Health Facility Committee, monthly financial reporting, procurement arrangements, drug stock-outs, infrastructure upgrading, staff incentives, reported leakage, service utilization and a composite accountability score. The facilities were equally distributed across the six geopolitical zones, with 46 facilities (16.7%) per zone. BHCPF funding received during the preceding 12 months ranged from approximately ₦1.6 million to ₦15.3 million. Annual account auditing was documented in 161 facilities (58.3%), while 115 (41.7%) had no documented annual audit. Accountability scores ranged from 1 to 10, demonstrating substantial heterogeneity in facility-level financial governance. Service utilization, measured as the percentage increase in antenatal-care attendance and deliveries compared with the preceding year, ranged from 0% to 84%. Descriptively, facilities with stronger combinations of annual auditing, functional community oversight and regular financial reporting were concentrated at the upper end of the accountability scale and generally recorded more favourable patterns of infrastructure upgrading, essential-drug availability, reported financial integrity and service utilization. Suspected fund diversion was concentrated among facilities with weaker accountability arrangements. Because the study was cross-sectional, the observed relationships are interpreted as associations rather than causal effects. The findings indicate that BHCPF financing is most likely to produce meaningful primary healthcare benefits when accompanied by effective auditing, transparent financial reporting, community oversight and procurement controls. Strengthening these accountability mechanisms is therefore essential for improving the value of BHCPF investments and advancing universal health coverage in Nigeria.