The relationship between environmental organizations and the corporate sector has gradually shifted toward the collaborative end, resulting in a broad array of "green alliances". In this paper, we focus on the strategies whereby environmental organizations seek to collaborate with private companies. In particular, we explore whether the ecophilosophy of an environmental organization-i.e., a set of values, attitudes, and beliefs about the natural environmentinfluences the selection of collaborative strategies. To address this question, we conducted two case studies of environmental organizations with a diverse ecophilosophy-namely, Greenpeace and WWF. In the cases, we covered a broad spectrum of collaborative strategies while also taking into account contextual factors with a possible influence on strategy selection. Building on our findings, we argue that ecophilosophy drives the selection of collaborative strategies and at the same time provides the lenses through which environmental organizations make sense of their operating context. We conclude by discussing the implications of our findings and by suggesting directions for future research on environmentalist-business collaboration.