This study examines the implementation gaps and outcome variations in Sustainable Development Goal 3 (Good Health and Well-Being) across Arusha Region, Tanzania, over the past five years. Using a mixed-methods approach combining national datasets, regional health reports, facility-level data, and interviews with health officials and frontline workers, the study analyzes progress in maternal and child health, service coverage, quality of care, and emerging health challenges. Findings reveal major national and regional gains—maternal mortality declined by nearly 80%, under-five mortality fell significantly, skilled birth attendance rose to 85%, and immunization coverage remained resilient. However, neonatal mortality stagnated, adolescent birth rates remained high, and the burden of non-communicable diseases increased sharply. Implementation assessments show strong service expansion but persistent human resource shortages, uneven penetration of SDG programmes into remote pastoralist communities, inadequate quality of neonatal care, and deep intra-regional inequities—particularly in Longido and Ngorongoro districts, where maternal and child health outcomes remain far below national averages. While Arusha City demonstrates strong performance due to better infrastructure and health-seeking behavior, rural districts continue to face supply gaps, socio-cultural barriers, and geographical isolation. The study concludes that although Tanzania and Arusha Region have made substantial progress toward SDG 3, achieving the 2030 targets will require intensified efforts to improve neonatal care, address adolescent reproductive health, strengthen NCD prevention, expand human resources, and implement culturally responsive interventions tailored to marginalized communities.