Purpose This study aims to explore how and what type of team diversity is related to team creativity in R&D organizations, incorporating conflict as a mediator and transformational leadership as a moderator. Design/methodology/approach Survey questionnaires were used to collect data from 24 Korean R&D teams (185 team members, 24 team leaders and 24 managers) in the public and private sectors. The dependent variable, team creativity, was measured by questioning R&D team managers to whom R&D team leaders report directly, and the antecedents, mediator and moderator were answered by team members and their leaders. Findings The data confirmed that team diversity, particularly informational diversity, was positively associated with team creativity. However, conflict did not show a significant mediating effect between team diversity and creativity. Transformational leadership had a negative moderating effect between informational diversity and task conflict in such a way that when transformational leadership was high, teams with higher informational diversity showed lower task conflict between team members. Originality/value A growing number of R&D projects require interdisciplinary efforts resulting in incorporating scientists and engineers from multiple disciplines, and growing numbers of women and minorities now choose careers in science and technology. Naturally, R&D project teams have become more diverse than before. This study provides empirical evidence from multiple sources, showing both mediating and moderating effects on the relationship between R&D team diversity and creativity.