Crowdsourcing (CS) provides access to external knowledge, and may be a relevant way to facilitate the innovation process of a company. In the open innovation paradigm (Chesbrough, 2003), innovation is the outcome of a coupling between outside-in and inside-out processes mobilizing the company and its partners. Therefore innovation can be understood in a business ecosystems logic. In this article, we use a case study to show how CS can be implemented to develop a business ecosystem. By mobilizing the literature on CS, business ecosystems and C-K theory, we emphasize the convergence between some of the success factors for CS and for the evolution of a business ecosystem: openness and modularity. In the studied case, CS contributes to the upstream phase of the development of a business ecosystem through the exploration of new concepts. JEL Codes: L80, 031, O32