People who successfully navigate life’s many challenges often do so through cooperative efforts. However, successful cooperation also relies on people’s ability to discern when, how, and with whom to invest their limited time and resources. Despite the centrality of cooperation to human flourishing, the ecological, cultural, and psychological mechanisms that facilitate cooperation require further investigation. Using a variety of methods — including surveys, experiments, longitudinal studies and field research — with diverse groups (e.g., American ranchers, Nicaraguan horticulturalists, nationally representative samples, multinational participants), I will present findings addressing three central questions: (1) Why do people cooperate? (2) What are the psychological mechanisms underlying cooperation? and (3) What are the consequences of cooperation for relationships, collective-risk management and well-being? Across several studies, I'll show how positive interdependence guides people’s cooperative motives, behaviors and other-oriented emotions (e.g., empathic concern). I will conclude by advancing and suggesting future directions based on a theoretical framework in which interdependence and cooperation act as mediating factors linking socio-ecological circumstances to social integration and well-being.