Cybervictimization and cyberbullying are serious public health issues. Parental monitoring serves as a protective factor, reducing adolescents’ risk of cybervictimization and cyberbullying. However, no study has systematically explored the interplay between parental monitoring, cybervictimization and cyberbullying at within-person processes, the mediating mechanisms between them, and the moderator of sex among Chinese adolescents. This study followed 2407 Chinese adolescents (50.23% girl, Mage = 12.75, SD = 0.58 at baseline) from seven schools over three time points across one year. Random intercept cross-lagged models were employed to investigate the dynamic links among parental monitoring, deviant peer affiliation, cybervictimization and cyberbullying. Results indicated significant associations among these variables at the between-person level. At the within-person level, parental monitoring, deviant peer affiliation, and cybervictimization were reciprocally predictable. Parental monitoring and deviant peer affiliation predicted cyberbullying, but cyberbullying did not predict parental monitoring or deviant peer affiliation. Additionally, parental monitoring indirectly predicted cybervictimization but not cyberbullying through deviant peer affiliation. Sex differences were observed in the longitudinal associations. The present study provides valuable insights into the relations among parental monitoring, deviant peer affiliation, cybervictimization and cyberbullying from a developmental perspective, offering a new scientific basis for interventions targeting adolescents’ involvement in cyberbullying.