Transcending the well-established and familiar boundaries of disciplinary silos poses challenges for even the most interpersonally competent scientists. This paper explores the challenges inherent in leading transdisciplinary projects, detailing the critical roles that leaders play in shepherding transdisciplinary scientific endeavors. Three types of leadership tasks are considered: cognitive, structural, and processual. Distinctions are made between leading small, co-located projects and large, dispersed ones. Finally, social-network analysis is proposed as a useful tool for conducting research on leadership, and, in particular, on the role of brokers, on complex transdisciplinary teams.