Boundary organizations are non-traditional structures that can foster transdisciplinary relationships and help catalyze the exchange of ideas, trust, and ultimately the implementation of scientific evidence into policy. Here, we describe GE-21, a group composed of researchers and public servants interested in promoting biodiversity and ecosystem services in Geneva, Switzerland, as an example of such a structure. GE-21 developed into a de facto social experiment for fostering inter- and transdisciplinary science and promoting nature-based policies. The results of two ecosystem-based projects carried by GE-21 were rapidly adopted into policy. Here, we provide a post-hoc narrative based on reports, interviews, and observations that collectively assess the merits and drawbacks of such structures for mainstreaming ecosystem services. We contend that the following five characteristics of this boundary organization may have facilitated its role as a conduit between academic research and public agencies: 1) projects proposing timely, relevant, and novel solutions to policy needs; 2) institutional support for applied interdisciplinary research; 3) a ‘safe space' to express ideas and develop close relationships over time; 4) availability of high-quality spatial data at a relevant scale, and scientific capacity to treat them; 5) resources dedicated to communication.