INTRODUCTION: Community health worker (CHW) interventions are promoted to improve maternal and newborn health in low-income and middle-income countries. We reviewed the evidence on their effectiveness in reducing socioeconomic inequities in maternal and newborn health outcomes, how they achieve these effects, and contextual processes that shape these effects. METHODS: We conducted a mixed-methods systematic review of quantitative and qualitative studies published between 1996 and 2017 in Medline, Embase, Web of Science and Scopus databases. We included studies examining the effects of CHW interventions in low-income and middle-income countries on maternal and newborn health outcomes across socioeconomic groups (wealth, occupation, education, class, caste or tribe and religion). We then conducted a narrative synthesis of evidence. RESULTS: We identified 1919 articles, of which 22 met the inclusion criteria. CHWs facilitated four types of interventions: home visits, community-based groups, cash transfers or combinations of these. Four studies found that CHWs providing home visits or facilitating women's groups had equitable coverage. Four others found that home visits and cash transfer interventions had inequitable coverage. Five studies reported equitable effects of CHW interventions on antenatal care, skilled birth attendance and/or essential newborn care. One study found that a CHW home visit intervention did not reduce wealth inequities in skilled birth attendance. A study of women's groups reported greater reductions in neonatal mortality among lower compared with higher socioeconomic groups. Equity was most improved when CHWs had relevant support for assisting women to improve health practices and access health care within community contexts. CONCLUSION: While current evidence remains limited, particularly for mortality, existing studies suggest that CHW interventions involving home visits, cash transfers, participatory women's groups or multiple components can improve equity in maternal and newborn health. Future mixed-methods research should explore intervention strategies and contextual processes shaping such effects on equity to optimise these efforts.