Abstract The National Health Insurance Scheme (NHIS), now re-established as the National Health Insurance Authority (NHIA) under the NHIA Act of 2022, was established in Nigeria to provide accessible, affordable, and equitable healthcare services and reduce out-of-pocket expenditure. Despite this mandate, rural communities continue to record low enrollment, estimated below 10%, and persistent coverage gaps that limit progress toward universal health coverage. This study examined the determinants of low enrolment and coverage gaps in the NHIS among rural communities in Niger State, Nigeria. Anchored on Rational Choice Theory, which posits that individuals make decisions based on perceived costs and benefits, the study assessed the influence of awareness, affordability, accessibility, and administrative processes on NHIS participation among rural residents. A descriptive survey research design was adopted. Data were collected using a structured questionnaire administered to 400 rural residents selected from Borgu, Lapai, Munya, Shiroro, and Wushishi Local Government Areas of Niger State, with 380 questionnaires retrieved and analyzed. Descriptive statistics and simple linear regression were used to analyze the data at a 0.05 level of significance. The findings revealed that awareness of the NHIS significantly influenced enrolment and coverage (R = 0.621, R² = 0.386, β = 0.621, p < 0.05). Affordability of contributions significantly affected enrolment (R = 0.584, R² = 0.341, β = 0.584, p < 0.05). Accessibility to NHIS-accredited healthcare facilities significantly influenced coverage (R = 0.667, R² = 0.445, β = 0.667, p < 0.05). Administrative and operational processes also had a significant effect (R = 0.603, R² = 0.364, β = 0.603, p < 0.05). All null hypotheses were rejected. The study concludes that low enrolment and coverage gaps constrain the effectiveness of the NHIS in rural Niger State. It is recommended that targeted community-based sensitization and enrollment drives be intensified to improve awareness, accessibility, and participation in the NHIS. Keywords: National Health Insurance Scheme, Low Enrolment, Coverage Gaps, Rational Choice Theory, Rural Communities, Niger State