An observational cohort study conducted in rural Tanzania from 2011 to 2015 examined the link between the strength of maternal, newborn, and child health care (MNCH) implementation and child survival rates. Utilizing data from health facilities’ service availability assessments and household surveys, the study assessed effective coverage of MNCH services. Through principal components analysis and mixed effects models, researchers identified independent scales of implementation strength. These scales were correlated with longitudinal data on child survival until December 31, 2015. Results indicated that increased implementation strength in general facility readiness and the provision of preventive MNCH and sick childcare services significantly reduced child mortality risks (HR = 0.59 and HR = 0.50, respectively). However, no significant effects were observed from the scale related to intrapartum care. The findings underscore the importance of robust implementation of antenatal, postnatal, and early childhood preventive services in accelerating reductions in child mortality. The study provides a methodological framework for leveraging routine data on service availability and readiness to evaluate health system strengthening and its impacts.