Background: The potential mechanisms underlying cyber victimization and the resulting psychological and physical symptoms remain unclear. Thus, the present study investigated whether Internet addiction mediates the association between peer victimization (e.g., cyberbullying) and psychological and physical symptoms. Furthermore, it was assessed whether physical exercise moderates the hypothetical mediation. Methods: 1854 students from 11 middle and high schools in Shenzhen, Guangdong Province, China, were sampled for this study. Psychological and physical symptoms were assessed using the World Health Organization Quality of Life-BREF, while Internet addiction was evaluated using the Internet addiction test by Young. Cyber victimization was measured using a single question. In addition, this study examined whether Internet addiction mediated the association between cyber victimization and both psychological and physical symptoms. Additional work was conducted to test if physical exercise played a moderating role in the mediation hypothesized above. Mediation and moderation were analyzed using PROCESS macro for SPSS. Results: Regression analysis showed that both cyber victimization (β = − 0.102, p < 0.05) and Internet addiction (β = − 0.278, p < 0.05) significantly predicted psychological and physical symptoms and demographic variables were controlled. Further mediation analysis suggested that Internet addiction mediated the relationship between cyber victimization and psychological and physical symptoms. The 95% CI (confidence interval) of the direct effect was (− 4.283, − 1.696) and the indirect effect (− 1.904, − 0.820), respectively, excluding zero. Finally, moderation analysis indicated that physical exercise moderated the relationship between Internet addiction and psychological and physical symptoms (p = 0.047). Conclusions: Internet addiction plays a mediating role in the association between cyber victimization and both psychological and physical symptoms, Thus, addressing Internet addiction among cyberbullying victims is worthwhile. Furthermore, physical exercise alleviates negative impacts on health and should thus be promoted.