The widespread use of the Internet among adolescents has led to cyberbullying. Bystanders play a vital role in sustaining and strengthening bullying. As trait mindfulness has been associated with prosocial behaviors, there is good reason to believe that there is a relationship between the mindfulness trait and the role adopted by cyberbullying bystanders. A cross-sectional study was employed with a sample of 2015 students aged 11-19 years. The participants completed the measures for cyberbullying, trait mindfulness, and their role as bystanders. The results revealed that 74.3% and 7.8% of them were identified as provictim and pro-perpetrator, respectively. MANCOVA was employed to analyze the differences in the characteristics of trait mindfulness according to the role of bystander with corrected age, and its use was significant for the following factors: Observing, describing, acting with awareness, and nonjudging. No significant differences were observed in the nonreactivity factor. Provictims and pro-perpetrators scored higher on observing than those who supported neither the victim nor the perpetrator. Implications and limitations are discussed.