This study examines the impact of generative AI (genAI) tools, specifically ChatGPT, on university student creativity across three disciplines: Marketing, Management, and Entrepreneurship. Using a randomised control trial design with 1190 undergraduate students, creativity was evaluated through fluency, originality, and elaboration. Findings reveal the use of ChatGPT had little to no effect for Entrepreneurship students yet tended to enhance creativity for Marketing and, to a lesser extent, Management students. However, its impact on originality was inconsistent, with improvements observed only in Marketing. Entrepreneurship students, with higher baseline creativity and potentially greater intrinsic motivation for the discipline, benefited less from genAI, suggesting a shift in its role from scaffolding tool to collaborative partner or productivity enhancer for students with these characteristics. The results highlight the need for educators to tailor genAI integration to disciplinary contexts and student needs. Additional research is required to explore how pedagogical factors, task and student proclivities shape genAI