Many researchers have separately developed instruments to measure environmental characteristics such as attitudes, values, and knowledge. However, there is no instrument used to measure all these aspects in one comprehensive instrument. This study is meant to develop and validate a green character instrument which reveals student behavior and awareness of the environment. The instrument consists of 40 statement items consisting of 5 aspects, namely private pro-environmental behavior, public pro-environmental behavior, environmental knowledge, environmental values, and environmental attitudes. It was implemented on 1,398 students from 15 universities in Indonesia. The instrument content validation was analyzed by three experts using content validity index (CVI). The construct validity was analyzed using exploratory factor analysis, confirmatory factor analysis, and RASCH analysis. The content validity results obtained CVI scores ranging between 0.8 and 0.9 with a good category, while item reliability was in a fairly good category with a high level of separation index. Construct validation resulted in 34 items (4 items were eliminated after Exploratory and Confirmatory Factor Analysis, and 2 items were eliminated after RASCH analysis) spread over five constructs, namely environmental behavior, environmental knowledge, environmental values, environmental attitudes, and environmental habits. The resulting instrument has a good level of item difficulty, with a well understood response set which can be understood easily by respondents, and without bias. Therefore, it can be used to measure the students' green character on both male and female.