We extend the knowledge-based perspective to consider the impact of spin-out founders on knowledge transfer to new ventures. We argue that existing theory largely ignores the founder's role as team catalyst who mobilizes a team and transmits the team's knowledge to a new venture. We address this gap by building theory on the role of a spin-out founder as a facilitator of co-mobility, and whose impact on firm outcomes is mediated by the size and organizational experience of the recruited team. The support for our hypotheses, through use of linked employee-employer US Census data from the legal services industry, has theoretical and practical implications for the knowledge-based view and human resource strategies for both existing and entrepreneurial firms.