Nigeria faces a high burden of preventable maternal deaths due to limited access to timely emergency obstetric care. The RESMAT initiative was established to reduce delays in accessing emergency maternal services. This study evaluated RESMAT's performance in referral timeliness, coordination, facility readiness, response times, and sustainability across five Nigerian states. A mixed-methods cross-sectional evaluation was conducted from March to May 2026 in Kano, Bauchi, Ogun, Ebonyi and Delta. Data sources included 112 structured questionnaires, 14 facility assessments, 84 facility-month referral records, and 10 dispatch logs. Over six months, 14 facilities reported 1,142 deliveries and 399 obstetric complications. RESMAT facilitated 479 emergency referrals (42 per 100 deliveries). Four maternal deaths occurred in Ogun State, despite completed referrals. Mean response time was 62.6 minutes, with only 2 of 10 dispatches arriving within 30 minutes. Facility assessments indicated 2 of 13 facilities lacked oxygen, 5 lacked blood transfusion services, and 6 lacked reliable electricity. Among RESMAT users, 95% found the service helpful and 70% would not have accessed care otherwise. RESMAT showed high referral completion and positive user feedback. However, the absence of baseline data limits the assessment of impact. Delayed transport payments, long distances to CEmONC facilities, inadequate infrastructure, and shortages of beds and supplies remain key challenges.