Cultivating the citizenship with environmental literacy who can take responsible environmental behavior to resolve environmental problem is the ultimate goal of environmental education. A competent teacher was important and related to the success of environmental education. Therefore, using the questionnaire method to investigate 82 in-service elementary school teachers, the purpose of this study was to understand in-service elementary school teachers' perceived knowledge and skills of environmental behavior, and to know how often they took environmental behavior in the last six-month period. The results indicated that the in-service elementary school teachers' perceived knowledge and skills of environmental behavior was not enough and need to be improved; the frequency of performing environmental behavior was very low and need to be cared. There were positive correlation among teachers' perceived knowledge, skills and performance of environmental behavior. Besides, the perceived skills of environmental behavior was a better predictor for taking environmental behavior than the perceived knowledge of environmental behavior.