Molloy, TracyWright, RichardXiong, Kangzhe2026-06-222026-06-222026http://hdl.handle.net/10292/21450This study explores, through a leadership lens, how the spirit of the game (SOTG) and the role of the spirit captain in ultimate frisbee (UF) influences the on and off-field behaviours and ethical development of UF athletes. SOTG is the moral cornerstone of UF, advocating fairness, self-refereeing and mutual respect among athletes. This study used mixed methods, combining quantitative survey data from 56 UF athletes in New Zealand with qualitative interviews with two UF organization leaders and two UF athletes to explore three objectives: the purpose of SOTG and the role of the spirit captain, their influence on athletes’ engagement in UF, and their influences on athletes’ behaviour in other sports and daily life. Quantitative research results show that athletes’ behavioural performance in adhering to the SOTG principle has significantly improved, especially in terms of rule knowledge and use, positive attitude and self-control, and fouls and body contact. At the same time, there is also a positive trend in respectful communication and fair-mindedness. Qualitative data indicates that SOTG helps cultivate athletes’ self-leadership, emotional regulation and moral reflection ability, while the spirit captain supports ethical conversation and shared responsibility. The athletes also said that they would apply behaviours based on SOTG, such as fairness, empathy and honesty, to other sports and daily life situations. These results confirm that SOTG is not only a rules-based ethical system but also a framework for promoting leadership and moral growth. This study expands previous research by providing empirical evidence from the UF community in New Zealand and linking SOTG with theories of ethics, shared leadership and self-leadership. The research results are of great significance for the future development of sports management, athlete education, and elite and Olympic-level self-refereeing sports.enThesisOpenAccess