Background: School bullying, the most common type of school violence, comprises a spectrum of aggressive behaviors that involve both perpetrators and victims. Objectives: The current study aimed to investigate the extent and nature of school bullying among middle school students in the North of Iran. Patients and Methods: A cross-sectional study was conducted on a sample of 834 Iranian middle school students. Participants completed a self-report anonymous questionnaire measuring bullying and victimization (Iranian-Olweus bullying questionnaire). Descriptive statistics and the Pearson's chi-squared test and multinomial logistic regressions with area, gender and grade variables were applied. Results: Prevalence rates of bullying behaviors based on the cut-off point at 2 or 3 times a month were 5.4% for only bully, 22.1% for only victim and 11% for both bully-victim. The prevalence of each form of victimization were 24.7% verbal, 15% relational, 10.3% physical and for each form of bullies 11% verbal, 5.3% relational, 6.4% physical. Boys were more involved in all forms of bullying behaviors. The students from rural areas were more involved in bullying .The most common places of victimization were the playground or athletic fields. The majority of victims were bullied by their classmates. Conclusions: Different forms of bullying have a distinct nature and the epidemiological pattern indicates that bullying exists in the Iranian schools. Thus, the effective bullying prevention and appropriate intervention programs are recommended.