Bullying, particularly among teenagers and young adults, is one of the most important issues facing school communities. At its very heart, this issue speaks to a troubling form of deviant behavior. When students engage in bullying behaviors, the effects are felt far beyond that of the direct victim. As such, it is important to investigate the etiology of such behavior in an effort to implement preventative practices. Accordingly, the main purpose of this study is to explain why students engage in bullying. Specifically, we use Wikström's situational action theory as a conceptual framework. A sample of 488 high school students (aged 15-18) from Rasht, Iran was used to test assumptions related to situational action theory, and the findings of this research generally demonstrated that the components of situational theory predicted students' bullying behavior. Moderating relationships in the situational action model indicated an interactive effect on bullying between criminal propensity and exposure to crime. Moreover, three-way interactions (personal morality--self-control--situational morality and personal morality--self-control--deterrence) yielded mixed statistical effects on bullying. Specific results, policy implications, study limitations, and directions for future research are discussed.