This study is designed to develop a certification system for non-formal environmental education educators as part of efforts to nurture non-formal environmental education educators, increase public trust in non-formal environmental education educators and secure structure and sustainability of non-formal environmental education. The job of non-formal environmental education educators-distant from technical expertise functions that are dealt with by existing certification system - belongs to education and service industry, And the certification system I try to develop is different from existing exclusive certification system based on written tests. It is rather an authentication system based on capability development. So its components are somewhat different from those of existing certification system. However, I also tried to ensure that the system should include components which were supposed to be part of basic certification system. The certification system for non-formal environmental education educators in the study is focused on developing a framework for basic certification system. Therefore, I believe that follow up studies may be needed to address execution, i.e., specific evaluation criteria to select organizations in charge of certification system and education course/program respectively, criteria to select instructors who will lead training course/program and decision on whether experiences as eco-guide or nature experience guide should be recognized as experiences for non-formal environmental education educator etc.