Introduction: Religious leaders are universally recognized as having an influence on immunization uptake and coverage in low- and middle-income countries (LMICs). Despite this, there is limited understanding of three questions: 1) how do religious leaders impact the uptake and coverage of immunization in LMICs? 2) what successful strategies exist for working with local faith actors to improve immunization acceptance? and 3) what evidence gaps exist in relation to faith engagement and immunization? Methods: In January 2021, we searched PubMed and Google Scholar databases covering the period from January 1, 2011, to January 15, 2021, with key search terms related to faith engagement and immunization in peer-reviewed literature and conducted a gray literature review to answer these three questions. We excluded articles covering faith engagement and immunization in high-income countries, news articles, online blogs, social media postings, and articles in languages outside of English. Data were coded to guide thematic analysis. Results: We found extensive evidence supporting the value of religious engagement for immunization promotion and acceptance in LMICs across faiths. However, there was limited rigorous evidence and examples of specific approaches for engaging local faith actors to strengthen immunization uptake in LMICs. As a result, there is a lack of widely shared knowledge of what works (or doesn’t) and successful models for engaging local faith actors.  Additional current evidence gaps include: few rigorous study designs; a lack of vaccine hesitancy studies outside of Nigeria and Pakistan; and limited exploration of faith engagement and immunization in religions other than Islam and Christianity. Conclusions: Our review findings reinforce the powerful role local faith actors play in diverse communities within LMICs in both promoting and inhibiting immunization uptake. The literature review comes at a critical time, given the urgent need to expand access to COVID-19 vaccination in LMICs. Findings from this review will advance understanding on how to more effectively engage local faith actors in promoting immunization campaigns and addressing vaccine hesitancy, which is more complex than expected. Further study is needed to understand how to most effectively counter vaccine hesitancy in different geographic, linguistic, and socio-cultural contexts.