BACKGROUND: Community engagement (CE) has been increasingly implemented across health interventions, including for maternal and newborn health (MNH). This may take various forms, from participatory women's groups and community health committees to public advocacy days. While research suggests a positive influence of CE on MNH outcomes, such as mortality or care-seeking behaviour, there is a need for further evidence on the processes of CE in different settings in order to inform the future development and implementation of CE across programmes. Communication is an integral component of CE serving as a link between the programme and community. The aim of the realist review described in this protocol is to understand how, why, to what extent, and for whom CE contributes to intended and unintended outcomes in MNH programming, focusing on the communication components of CE. METHODS: Realist review methodology will be used to provide a causal understanding of what communication for CE interventions in MNH programming work, for whom, to what extent, why, and how. This will be done by developing and refining programme theories on communications for CE in MNH through a systematic review of the literature and engaging key experts for input and feedback. By extrapolating context-mechanism-outcome configurations, this review seeks to understand how certain contexts trigger or inhibit specific mechanisms and what outcomes this interaction generates when communication in CE interventions is used in MNH programming. DISCUSSION: A realist philosophy is well-suited to address the aims of this study because of the complex nature of CE. The review findings will be used to inform a realist evaluation case study of CE for an MNH programme in order to ascertain transferable findings that can inform and guide engagement activities in various settings. Findings will also be shared with stakeholders and experts involved in the consultative processes of the review (through workshops or policy briefs) in order to ensure the relevance of these findings to policy and practice. SYSTEMATIC REVIEW REGISTRATION: PROSPERO CRD42022293564.