This article starts from the premise that, due to a lack of dedicated incentives as well as the size of the population, International Non-Governmental Oragnzations (INGOs) are more likely to compete than to cooperate. Drawing upon collective action and principal-agent theories, this research provides a field-level perspective on INGOs' cooperative strategies. Building on an analysis of two very diverse cases (human rights protection in Kosovo and humanitarian activities in Somalia), data collected through field research have led to a distinction between coordination, which depends on the provision of incentives and constraints by donors, and cooperation, which relies on trust and on pursuing common interests among INGO members. Overall, it appears that INGOs pursue a creative mix of strategies: competition, formal coercive coordination and informal trust-based cooperation. This paper concludes with a discussion of the results through the insights they provide on issues related to the fragmentation, efficiency and inclusiveness of the crisis response.