Purpose: Educational institutions have a special social responsibility to initiate processes of sustainability transformation in society, nevertheless, activities that effectively address students as well as employees are rather moderate. To initiate change alongside strategic and political decisions, this paper aims to present findings of a gamification intervention (hereafter referred to as "climate duel"), which was implemented in a field study and tested to assess its potential as a supporting and transformative approach in a university context. Design/methodology/approach: A three-month field study was conducted with two universities of applied sciences. The study included an environmental impact analysis of the two participating university departments, the conception and testing of the intervention and associated surveys to evaluate the effectiveness of the intervention in order to and to obtain feedback that would allow the duel to be scaled up at other universities or institutions. Findings: Three hundred seventy-five people took part and saved 2.6 tons of greenhouse gas emissions through their participation in the "climate duel" and their corresponding behavioural changes. In addition, feedback from the participants yielded positive results in terms of behavioural changes and generated valuable evidence for future implementations. Nevertheless, there is still room for improvement, especially in terms of supporting communication activities that promote social relatedness to motivate each other, share experiences or deal with implementation difficulties in everyday life. Originality/value: Building on the promising effects of gamification, the study is a showcase for applied science. With the possibility of testing a theory-based intervention in practice, an implementable, effective and scalable measure for universities that helps to accelerate the transformation process is available.