This study examined the influence of Primary Health Care (PHC) service quality on maternal and child health (MCH) outcomes and its implications for the attainment of Universal Health Coverage (UHC) in Kogi State, Nigeria. The study was necessitated by persistent challenges in the quality of PHC services, including inadequate availability of essential medicines, prolonged waiting times, poor patient-provider interactions, infrastructure deficiencies, and uneven access to skilled health personnel, which continue to undermine maternal and child health outcomes. The study adopted a descriptive cross-sectional survey design. The population comprised residents and PHC users in six selected Local Government Areas across the three senatorial districts of Kogi State, with a combined population of 1,344,493. A sample size of 400 respondents was determined using Taro Yamane's formula, while a multi-stage sampling technique was employed. Data were collected through structured questionnaires and semi-structured key informant interviews. Of the 400 questionnaires administered, 372 were correctly completed and returned, representing a 93% response rate. Quantitative data were analyzed using descriptive statistics and simple linear regression, while qualitative data were subjected to thematic analysis. The findings revealed that 60.2% of respondents perceived PHC health workers as competent, while 51.1% reported inadequate availability of drugs. Similarly, 53.8% expressed satisfaction with hygiene standards, although 50.5% reported concerns regarding respectful treatment of patients. Furthermore, 71.5% of respondents agreed that PHC services had improved maternal and child health, 76.3% reported improved immunization coverage, and 72.6% affirmed the effectiveness of PHC in promoting preventive healthcare. The regression analysis established a significant positive relationship between PHC service quality and MCH outcomes (R = 0.687, R² = 0.472, F(1,370) = 330.608, p < 0.001). The regression coefficient (B = 0.673; β = 0.687; t = 18.182; p < 0.001) indicates that improvements in PHC service quality significantly predict better maternal and child health outcomes. The study therefore rejected the null hypothesis and concluded that quality PHC services are critical to improving MCH outcomes and advancing UHC in Kogi State. The study recommends sustained investment in PHC infrastructure, essential medicines, skilled health personnel, patient-centred care, maternal and child health services, routine immunization, preventive healthcare, and equitable resource allocation, particularly in rural and underserved communities. Strengthening these dimensions of PHC will contribute to improved health outcomes, equity, financial protection, and the broader attainment of UHC in Kogi State.