Whereas defending victims can put an end to school bullying incidents, few witnesses engage in such behavior. This study aimed to explore the intention to defend victims among distinct witness profiles based on behavioral and psychological characteristics. Within the framework of the theory of planned behavior, we measured intentions, attitudes, subjective norms, perceived behavioral control to defend victims, and past reactions to bullying among 276 middle school students (55.1% male, M[subscript age] = 13.1, SD = 1.22) who had witnessed bullying. A cluster analysis identified five witness clusters. Although "prodefense," "antidefense" and "probullying" witnesses are characterized by a coherent behavioral-psychological profile in favor of or against victim support, "conflicting beliefs' witnesses" and "inconsistent witnesses" interestingly showed a beliefs conflict or psychological-behavioral gap that has never been identified before. Beyond elucidating witness characteristics, this study offers new prevention avenues adapted to each profile's deficits.