ABSTRACT This study aimed to investigate the prevalence of online victimisation, the prevalence of stress among high school students, and the mediating role of avoidance coping in the online victimisation-stress relationship. A cross-sectional study utilising 507 high school students was conducted employing a convenience sampling method. The survey comprised questions related to online victimisation, avoidant coping, stress, and socio-demographics. Research results showed that the prevalence of online victimisation and stress among high school students were 59.2% and 40.8%, respectively. Online victimisation directly increased stress levels among students (β = 0.213, p < 0.001). Avoidant coping mediated the online victimisation-stress relationship (β = 0.383, 95% CI = [0.276; 0.509]). The findings of this study are a practical basis for proposing intervention measures to reduce stress for high school students in the study area.