This thesis examines mushrooms in contemporary art and considers the ecological, social and aesthetic implications embedded in interkingdom relationships. I have chosen to focus specifically on participatory and relational artworks, thus I consider the ways in which leading art critics, theorists and writers such as Claire Bishop, Grant Kester, Nato Thompson and Nicolas Bourriaud have approached relational art. My investigation is based on two case studies: Carsten Höller’s installation Soma (2010) at the Hamburger Bahnhof in Berlin; and the performative mushroom foray Terrestrial/Celestial (2010) enacted by Toronto-based artist Diane Borsato. These works employ elements of mycology to underscore the workings of fungi in the natural ecosystem, thus enabling a nuanced understanding of who is relating to whom within the given encounter and to what effect. Ultimately the notion of symbiosis is central to this analysis. Furthermore, I situate these works within posthumanist theory and compare Gilles Deleuze and Félix Guattari’s notion of the rhizome to a research/artistic methodology based on mycology. Given the myriad of art projects that employ non-human subjects, an understanding of symbiosis can inform essential questions that surround collaborative, participatory, and relational art practices today.