© 2019 The Author(s).Background: The global refugee crisis has become central to health and policy debates. There is a growing need to investigate how acculturation impacts mental health among asylum seekers and refugees. Many forced migrants have an increased risk of experiencing negative mental health outcomes, but this review will only assess the current literature on acculturation and mental health among adults. Research questions include the following: (1) How is acculturation conceptualised? (2) What are the most salient mental health outcomes? (3) How are acculturation and mental health measured and related? and (4) How do macrostructural factors affect the relationship between mental health and acculturation? Methods: We will use a meta-narrative approach to synthesise the breadth of acculturation and mental health literature from various research traditions. This review will include empirical studies measuring variations of acculturation and mental health among adult forced migrants from low- A nd middle-income countries residing in high-income countries. Studies will be retrieved from the following academic databases: MEDLINE, Embase, PsycINFO, Global Health, ProQuest Social Science and Web of Science. Additional studies will be collected from King's College London's online library databases and e-resources, and reference lists of eligible studies. Studies from database inception and written in English will be included. All full-text papers will undergo quality appraisal using the Mixed Methods Appraisal Tool (MMAT). Extracted data will be analysed using a conceptual framework analysis to construct overarching narratives and a framework that will describe the relationship between acculturation and mental health. Discussion: A meta-narrative systematic review provides a flexible and systematic approach to synthesising the heterogeneous literature on acculturation and mental health. This review will guide the development of a conceptual framework to aid future research on acculturation among adult forced migrants. As high-income countries seek to integrate forced migrants into society and improve their access to vital resources, this review has the potential to transform policies and practices that influence migrant mental health.