This paper aims to examine the ecosystem of worker cooperatives in Italy, Mondragon, and France. The worker cooperatives in the three regions have quite developed as compared to those in other countries. The research has identified three major shortcomings that hinder the growth of worker cooperatives: collective decision making costs, dual risk that worker members must take, and difficulties associated with measuring performance of management or workers. The investigation on the three cases reveals that the three regions share common features in ecosystem of worker cooperatives: the adequate role of federation to deal with collective decision making costs in primary worker cooperatives, development of financial system to resolve the dual risk, and operation of education and training programs to nurture cooperative leaders. Lastly, implications for development of worker cooperatives in Korea are offered.