Résumé : This paper investigates whether financial cooperatives are crowded out by commercial banks in the process of financial sector development. We use a self-constructed database (1990-2011) of financial cooperatives in 55 developing countries. Our empirical results are threefold. First, financial cooperatives tend to reach more members in countries where the commercial banking sector is weak. This validates their role as a market failure solution. Second, in the process of commercial bank expansion, financial cooperatives run the risk of being crowded out. Third, financial cooperatives seem to benefit from some kind of bank presence, especially as far as savings mobilization is concerned.