This research was aimed at finding out whether Decision Making was good as a mediated factor between Organizational Culture, Locus of Control, with students’ Environmental Protection Behavior(EPB). A causal survey used by selecting 130 randomly University’ students. There were four instruments measured Organizational Culture (24 items, rel .872), Locus of Control (23 items, rel .822), Decision Making (23 items, rel .837), and Environmental Protection Behavior (25 items, rel .870). Data analyzed by path analysis. The research results showed that Organizational Culture, Locus of Control and Decision Making directly and significantly affected EPB, then Organizational Culture andLocus of Control indirectly but nonsignificantly affected EPB as well. Therefore, Decision Making was, in this case, a good mediator. Based on those results, it could be concluded that if environmental protection behavior would like to be improved positively, therefore, organizational culture, locus of control, and students’ decision making ability should be minimized its variation by introducing and offering an integrated environmental education compulsory for all students level.Keyword:Locus of Control, Environmental Protection Behavior, path analysis, and mediator.