Objective: The purpose of this study was to determine the effect of Aggression Management Training Program (AMTP) on knowledge levels and aggression perceptions of nurses working at psychiatric inpatient clinics in Kayseri/Turkey. Methods: This study was conducted with 27 nurses who participated to the AMTP as the one group pretest-posttest experimental design. Data were collected by using Personal Information Form, Perception of Aggression Scale, and Assessment Form of Knowledge Levels of Nurses Regarding Aggression Management. AMTP was carried out interactively with totally 3 groups including 2 groups (10 participants in each group) and 1 group of 7 participants. Knowledge levels and perceptions of aggression of nurses were evaluated before, after and three months after AMTP. Results: In this study, AMTP was found to increase knowledge level of nurses and led to positive changes at their aggression perceptions. Conclusion: Consequently, it was determined that AMTP increased knowledge levels of nurses working at psychiatric clinics and provided positive changes at their aggression perceptions. It could be recommended to continue training on aggression management with regular intervals.