BACKGROUND AND OBJECTIVES: Bullying victimization is strongly associated with sleep quality issues in primary school students, yet the underlying mechanisms among these variables require further exploration. This study investigates the mediating role of mobile phone addiction and the moderating role of physical activity in the relationship between bullying victimization and sleep quality among primary school students, contributing to a deeper understanding of these psychological processes. METHODS: This study utilized a convenience sampling method to recruit 502 primary school students in 2023. The sample included 232 boys and 270 girls, with ages ranging from 10 to 12 years (mean age = 11.15 ± 0.62). Participants were recruited from specific region or school district to ensure a diverse representation of the target population. Ethical approval was obtained from the relevant institutional review board, and informed consent was obtained from both the students and their parents or guardians prior to data collection. RESULTS: Bullying victimization was significantly positively correlated with both sleep quality issues and mobile phone addiction. Additionally, mobile phone addiction was significantly positively correlated with sleep quality issues. The analysis confirmed that mobile phone addiction mediates the relationship between bullying victimization and sleep quality. Furthermore, physical activity was found to moderate the relationship between bullying victimization and mobile phone addiction. CONCLUSIONS: This study elucidates the psychological mechanisms underlying the relationship between bullying victimization and sleep quality among primary school students. Mobile phone addiction serves as a mediating factor, while physical activity acts as a moderating factor in the link between bullying victimization and mobile phone addiction. These findings underscore the importance of addressing mobile phone addiction and promoting physical activity as part of targeted interventions to improve sleep quality among primary school students.