Evidence synthesis (ES) has emerged as a key research method within the social and behavioral sciences. Academic librarians, as experts on information search and retrieval, are often highly valued contributors to faculty ES projects. While many libraries have formed team-based ES services to support researchers, and have discussed insights from these models, very little has been shared by or about librarians who offer ES services outside of a team-based approach. This article seeks to address this knowledge gap by expanding upon a model for a single-librarian ES service, and sharing key insights for others who may wish to develop ES library services in non-health science contexts. The service model pays particular attention to the proactivity and boundaries single-librarian evidence synthesis service providers might use in order to best support a wide number of researchers while maintaining a sustainable evidence synthesis service, librarianship, and work-life balance.