Contemplative technologies in the form of Buddhist practices that challenge the sense of self and thereby enhance the experience of interrelationality are viable strategies for addressing existential concerns such as the environmental crisis. Much of the existing research on Buddhism and ecology neglects to measure environmentally sustainable behavior or engage with empirical research. Likewise, experiments measuring the effects of contemplative practice on oxytocin, a neuropeptide hormone often implicated in interrelational contexts, are scarce. This study explores the existential relevance of Chan and Huayan practices for oxytocin and environmentally sustainable behavior. Using empirical methods, it reports on an experimental fieldwork study among international participants in a one-month retreat at a Buddhist monastery in Taiwan. Salivary oxytocin, recycling, and food waste were measured, while phenomenological reports of experiences during contemplative practice were also obtained. Results of enzyme-linked immunosorbent assay indicate a marginal increase in oxytocin following Chan practice of the huatou “Who recites the Buddha’s name?” which targets the sense of self, consistent with phenomenological reports reflecting an interrelational, ecological sense of self through huatou. Results also indicate increased recycling and decreased food waste by mass as a function of time on retreat. While the precise mechanisms explaining why participants exhibited more environmentally sustainable behaviors are currently unclear, the discussion proposes an empirically testable framework for bridging ecologies that links emotion, sense of self, and behavior. Contemplative practices may contribute to changes in oxytocin and environmentally sustainable behavior through activation of existential, aesthetic emotions such as doubt and awe, thereby inducing changes in the practitioner’s sense of self, which they may then experience as interrelated with broader ecologies, a possibility awaiting further research. The huatou fieldwork and proposed follow-up study on the Huayan sanmei men thus shed light on the relevance of contemplative technologies from Chinese Buddhism for bridging ecologies in the existentially relational sense.