Animal societies in which some individuals forgo their own reproduction and help others to reproduce are one of the most remarkable products of evolution. The evolution of animal societies can be usefully thought of in three stages: social group formation, the processes that bring individuals together; social group maintenance, the processes that keep individuals together; and social group transformation, the processes that convert simple groups into more complex groups. Anemonefishes form simple groups composed of a breeding pair and a small number of non-breeders. As such, they present exciting opportunities to test the robustness of current theories of social evolution and generate new insights, using relatively understudied taxa (fishes) in a relatively understudied environment (the sea). This chapter reviews what is known, and what is not yet known, about anemonefish social group formation, maintenance, and transformation. This review provides a framework for thinking about anemonefish social evolution, laying the foundations for future investigators as they become a model system for marine science.