This paper outlines a collective action approach to study nongovernmental organizations (NGOs). We contend that while political scientists and sociologists have extensively written about NGOs, they have not systematically examined fundamental collective action issues such as why and where NGOs emerge, how they function, how they are structured, and what strategies they employ to mitigate agency conflicts and ensure accountability. Instead of theorizing about NGOs as a category, NGO scholars have developed descriptive typologies relevant to study small subsets of the NGO population. In contrast, the non-profit literature, which studies broadly the same actor category, has systematically focused on fundamental questions inherent in any collective endeavor. We conclude that by employing a collective action perspective, specifically the theories of firm, NGO scholars will be able to develop explanations about NGO origin, structure, and strategy that have superior explanatory power and are generalizable across NGOs.