Although public engagement in research is increasingly popular, the involvement of citizens living in vulnerable circumstances is rarely realized. This narrative review aims to describe and critically analyse concerns and corresponding strategies, tools, and methods that could support the inclusion of these citizens in health research. The 40 studies that are included were thematically analysed using the socioecological model. Concerns originate most often on the intrapersonal level of the socioecological model, but concerns were also identified at institutional, community, and policy levels. It is thought-provoking that there is a lack of attention for the research and policy structure in which engagement practices are designed, implemented and evaluated. More research is needed to explore how these cultures could be changed in a way that promotes rather than restrains the engagement of citizens living in vulnerable circumstances in research and policymaking.