Both anthropologists and ecologists have increasingly recognized the need to reach beyond their own disciplinary frameworks when handling processes of marginalization that involve intersecting social–ecological dimensions, particularly as global environmental challenges force humans and wildlife into new and challenging conditions. In this letter, we suggest a cross-disciplinary framework for studying the social–ecological margins. We highlight two definitions of marginality, one from the social sciences and one from the natural sciences, and discuss the relations that render a research subject marginal through four case studies on wildlife and agriculture. This discussion illuminates the importance of studying the behavioral and cultural repertoires with which marginal populations respond to social–ecological constraints.