Beginning in about 1990 and continuing into the present, an international network of researchers has developed and tested a methodology for integrating complex systems theories into sustainable development projects. Drawing on a theoretical understanding of complex systems and combining it with Checkland’s Soft Systems Methodology and best practices of community engagement drawn from a wide variety of sources, we have developed a methodology that is theoretically sound and practically effective. AMESH, an Adaptive Methodology for Ecosystem Sustainability and Health, has emerged from, and been tested in, Nepal, Kenya, Canada, and Peru.