The purpose of this study was to explore the structural relationships among mobile game addiction, cyberbullying, and hostility with elementary school students and to identify the specific pathways through which mobile game addiction affects cyberbullying perpetration. A total of 406 students at grades 4 to 6 were recruited from two elementary schools in a metropolitan area. The participants were surveyed regarding their levels of mobile game addiction (MGA), cyberbullying victimization (CBV), cyberbyllying perpetration (CBP), and hostility. Using the bootstrapping analysis in the structural equation modeling (SEM), pathways through which mobile game addiction affects cyberbullying perpetration were tested. The results are as follows. Firstly, mobile game addiction had a direct effect on cyberbullying victimization and an indirect effect on cyberbullying perpetration. Secondly, three pathways from mobile game addiction to cyberbullying perpetration were identified in a path analysis: ‘MGA → CBV → CBP,’ ‘MGA → hostility → CBP,’ and ‘MGA → CBV → hostility → CBP.’