This study investigated the associations of psychological and social variables with the likelihood of exhibiting three different behaviors as a bystander in a bullying situation. The sample comprised 238 Korean-American and Korean students, from the 3rd to 12th grades, studying in the USA. Students receiving classmate support showed a lower probability of exhibiting outsider behaviors in a bullying situation as compared to non-involvers, whereas those receiving teacher support showed less likelihood of exhibiting assistant, outsider, and defender behaviors as compared to non-involvers. Furthermore, students showing higher responsibility exhibited a lower probability of being a defender group as compared to the non-involvers, while those showing higher empathy demonstrated a greater probability of being in the defender group over non-involvers. The current study discusses the implications for bullying preventive interventions in school settings. (Contains 2 tables.)