Mentoring research and development often uses a mentor-protégé model, but research often takes place in teams. In this exploratory study, the authors identify the structures and prevalence of multi-mentoring teams by surveying undergraduate researchers about the people who helped them and the support they received. Research teams were common, and interdisciplinary projects involved more mentors. Faculty were more often considered mentors than others, and those providing information and appraisal were more often mentors than those providing psychosocial support. Students with multiple mentors received more support than those with one or none. Natural science projects experienced higher rates of both mentorship and multi-mentoring, which carries implications for student and faculty development.