Abstract. We develop and test a theoretical model that explains how collective psychological ownership—shared feelings of joint possession over something—emerges within new creative teams that were launched to advance one person’s (i.e., a creative lead’s) preconceived idea. Our model proposes that such teams face a unique challenge—an initial asymmetry in feelings of psychological ownership for the idea between the creative lead who conceived the idea and new team members who are beginning to work on the idea. We suggest that the creative lead can resolve this asymmetry and foster the emergence of collective psychological ownership by enacting two interpersonal behaviors—help seeking and territorial marking. These behaviors build collective ownership by facilitating the unifying, centripetal force of team identification and preventing the divisive, centrifugal force of team ownership conflict. Our model also proposes that collective ownership positively relates to the early success of new creative teams. The results of a quantitative study of 79 creative teams participating in an entrepreneurship competition provided general support for our predictions, but also suggested refinements as to how a creative lead’s behavior influences team dynamics. The findings of a subsequent qualitative investigation of 27 teams participating in a university startup launch course shed additional light on how collective ownership emerges in new creative teams launched to advance one person’s idea.