This study examined the relationships between children's mobile gaming preferences, online risks, and mental health. Data were obtained from a sample of 2,702 third and fourth grade students from 16 elementary schools in Taiwan and 9 schools in China. A self-administered questionnaire was used. The mental state of the children who participated in the study was assessed using the Strengths and Difficulties Questionnaire (SDQ), while mobile gaming addiction was assessed using the short form of the Internet Gaming Disorders Scale (IGDS9-SF). The results showed that about 54% of children played mobile games with others (multi-player), while 31% played mobile games alone, and 15% did not play mobile games. Multiple logistic regression results indicated that behaviors such as participating in multi-player games, playing violent games, a poor parent-child relationship, and living in a rural area were associated with a greater risk of mobile gaming addiction. Involvement in multi-player games, playing violent games, mobile gaming addiction, and exposure to mobile violence/pornography were associated with greater risks of cyber aggression/victimization. Multiple regression results showed that being a multi-player, playing violent games, mobile gaming addiction, exposure to violence/pornography, exposure to cyber aggression/victimization, and having a poor parent-child relationship were associated with emotional and behavioral problems.