The aim of this study was to identify the classes of trajectory in mobile phone dependency using growth mixture modeling among Korean early adolescents from elementary school to the middle school transition. The effects of negative parenting on determining the classes were also examined. The participants were 2,378 early adolescents in the Korean Children and Youth Panel Survey. Three classes of trajectory in mobile phone dependency were found. Adolescents who were highly dependent on mobile phones were very few and most Korean adolescents were not serious with regard to mobile phone dependency. Although there was a large difference in mobile phone dependency among three classes at the very early period of adolescence, it decreased over time and all adolescents showed moderate level of mobile phone dependency. In addition, a multinomial logistic regression analysis showed that negative parenting was a significant predictor of determining the classes. The findings provided important implications for intervention and prevention of mobile phone dependency during early adolescence.