In 2020, the lockdown during the COVID-19 pandemic exacerbated the vulnerability of the most marginalized people in French Guiana by making it even more difficult for them to access healthcare and their rights. To combat this additional inequality, Médecins du Monde (MdM) launched an emergency program in Cayenne and, as part of this effort, recruited 13 peer health mediators—that is, individuals from the communities they serve. An evaluation of this initiative shows that the mediation approach is a key element in reducing inequalities in access to rights and healthcare and in facilitating access to information and prevention. It highlights the crucial role of mediators, who help better understand the specific needs and vulnerabilities of the people they support.