This study explores the mechanisms that enable a group of co-founders to successfully transition to a founding team. Employing techniques of process research—grounded theory and temporal bracketing—we study five groups of co-founders who banded together during an entrepreneurship learning program in Norway to start a venture. Following these groups from the beginning of their formation throughout a period of 17 months, we observe the conditions that stimulate members’ bonding processes. Our findings suggest a complex and dynamic interplay of mechanisms and properties that guide the transition from a group of co-founders to a founding team. These properties emerge as collective entities that team members cultivate as result of their interaction over time and significantly affects the content of team processes. Keywords: Co-founders; groups and teams; new venture development; team development