This article presents a framework for developing internally sustainable evaluation systems for environmental education organizations, although the framework can be applied to other types of organizations. The authors developed a sustainable evaluation framework (SEF) with the intent of creating an evaluation system that could be self-administered by the staff of an environmental education organization in perpetuity. Key components of the framework include that it is utilization-focused (designed specifically for the needs of its users), participatory (empowering the users at each step of the design and implementation process), theory-driven (employing logic modeling and consulting relevant literature for concept clarification), and consumer-based (directly addressing the needs of probable audiences of evaluation results). The article illustrates the evaluation framework and its key outcomes using a case study from the Great Smoky Mountains Institute at Tremont (GSMIT), where the authors facilitated the development of an evaluation system. In addition to the creation of a credible, adaptable, and sustainable system, outcomes of the framework's implementation included clarification of organizational goals, enhanced organizational commitment from staff, professional development, and new prospects for adaptive management. (Contains 3 figures and 4 footnotes.)