The main problem faced by every country in the world is environmental problems which are assumed to be brought about by human activities as mentioned by IPCC reports since 1995. That was why this research has been conducted to get information scientifically on whether human behavior, in this case, students’ pro-environmental behavior (PEB) might be affected by their knowledge of ecosystem (KE) and mediated by their intention to act toward the environmental issues (ITA). Therefore, a causal survey was carried out involving 200 senior high school students around Bekasi, Indonesia, as a sample. There were three instruments developed which measured students’ PEB, KE, and ITA. Data were analyzed by path analysis. The research results showed that students’ KE and ITA were found directly and significantly affected their PEB, however, students’ KE did not prove that its effect on ITA was significant. So, it could be concluded that ITA, in this case, was not a good and significant mediator between KE and students’ PEB. Based on these findings, it could be implied that in trying to minimize students’ PEB variation, therefore, factors such as students' knowledge about the ecosystem and intention to act toward the environment, should be considered to be empowered among students throughout school system policies. Keyword : Pro-environmental Behavior, Intention to Act, Path Analysis.