OBJECTIVES: To examine socioeconomic and health system determinants of wealth-related inequalities in neonatal mortality rates (NMR) across 48 low- and middle-income countries. METHODS: We used data from Demographic and Health Surveys conducted between 2006 and 2012. Absolute and relative inequalities for NMR and coverage of antenatal care, facility-based delivery, and Caesarean delivery were measured using the Slope Index of Inequality and Relative Index of Inequality, respectively. Meta-regression was used to assess whether variation in the magnitude of NMR inequalities was associated with inequalities in coverage of maternal health services, and whether country-level economic and health system factors were associated with mean NMR and socioeconomic inequality in NMR. RESULTS: Of the three maternal health service indicators examined, the magnitude of socioeconomic inequality in NMR was most strongly related to inequalities in antenatal care. NMR inequality was greatest in countries with higher out-of-pocket health expenditures, more doctors per capita, and a higher adolescent fertility rate. Determinants of lower mean NMR (e.g., higher government health expenditures and a greater number of nurses/midwives per capita) differed from factors associated with lower NMR inequality. CONCLUSIONS: Reducing the financial burden of maternal health services and achieving universal coverage of antenatal care may contribute to a reduction in socioeconomic differences in NMR. Further investigation of the mechanisms contributing to these cross-national associations seems warranted.