Globally, increasing efforts have been made to hold duty-bearers to account for their commitments to improve reproductive, maternal, newborn, child and adolescent health (RMNCAH) over the past two decades, including via social accountability approaches: citizen- led, collective processes for holding duty-bearers to account. There have been many individual studies and several reviews of social accountability approaches but the implications of their findings to inform future accountability efforts are not clear. We addressed this gap by conducting a review of reviews in order to summarise the current evidence on social accountability for RMNCAH, identify factors contributing to intermediary outcomes and health impacts, and identify future research and implementation priorities. The review was registered with the International Prospective Register of Systematic Reviews (PROSPERO CRD42019134340). We searched eight databases and systematic review repositories and sought expert recommendations for published and unpublished reviews, with no date or language restrictions. Six reviews were analysed using narrative synthesis: four on accountability or social accountability approaches for RMNCAH, and two specifically examining perinatal mortality audits, from which we extracted information relating to community involvement in audits. Our findings confirmed that there is extensive and growing evidence for social accountability approaches, particularly community monitoring interventions. Few documented social accountability approaches to RMNCAH achieve transformational change by going beyond information-gathering and awareness-raising, and attention to marginalised and vulnerable groups, including adolescents, has not been well documented. Drawing generalisable conclusions about results was difficult, due to inconsistent nomenclature and gaps in reporting, particularly regarding objectives, contexts, and health impacts. Promising approaches for successful social accountability initiatives include careful tailoring to the social and political context, strategic planning, and multi-sectoral/multi-stakeholder approaches. Future primary research could advance the evidence by describing interventions and their results in detail and in their contexts, focusing on factors and processes affecting acceptability, adoption, and effectiveness.