BackgroundOver 240 million children live in countries affected by conflict or fragility, and such settings are known to be linked to increased psychological distress and risk of mental disorders. While guidelines are in place, high-quality evidence to inform mental health and psychosocial support (MHPSS) interventions in conflict settings is lacking. This systematic review aimed to synthesise existing information on the delivery, coverage and effectiveness of MHPSS for conflict-affected women and children in low-income and middle-income countries (LMICs).MethodsWe searched Medline, Embase, Cumulative Index of Nursing and Allied Health Literature (CINAHL) and Psychological Information Database (PsycINFO)databases for indexed literature published from January 1990 to March 2018. Grey literature was searched on the websites of 10 major humanitarian organisations. Eligible publications reported on an MHPSS intervention delivered to conflict-affected women or children in LMICs. We extracted and synthesised information on intervention delivery characteristics, including delivery site and personnel involved, as well as delivery barriers and facilitators, and we tabulated reported intervention coverage and effectiveness data.ResultsThe search yielded 37 854 unique records, of which 157 were included in the review. Most publications were situated in Sub-Saharan Africa (n=65) and Middle East and North Africa (n=36), and many reported on observational research studies (n=57) or were non-research reports (n=53). Almost half described MHPSS interventions targeted at children and adolescents (n=68). Psychosocial support was the most frequently reported intervention delivered, followed by training interventions and screening for referral or treatment. Only 19 publications reported on MHPSS intervention coverage or effectiveness.DiscussionDespite the growing literature, more efforts are needed to further establish and better document MHPSS intervention research and practice in conflict settings. Multisectoral collaboration and better use of existing social support networks are encouraged to increase reach and sustainability of MHPSS interventions.PROSPERO registration numberCRD42019125221.