The Social bonding theory assumes that social ties are closely associated with maladaptive behavior, and this theory may be applied to explain the smartphone dependence in adolescence. The purpose of this study was to verify how school adjustment mediated the relationship between the parental neglect and smartphone dependence. The data from Korean Children and Youth Panel Survey were utilized in this study. Participants were 2280 students in the 2nd year of middle school [male 1152, female 1128; 13.89 years (SD = 0.34)] who were followed up for four years. We conducted a Multivariate Latent Growth Modeling (LGM) to verify the relationships between variables. In addition, mediating effect was analyzed using the Bootstrapping Test. Findings indicated that parental neglect was negatively associated with school adjustment in the first wave, and school adjustment showed a greater decrease as parental neglect indicated a greater increase. In addition, school adjustment was negatively associated with smartphone dependence in the first wave, and smartphone dependence showed a greater decrease as school adjustment indicated a greater increase. Mediating effect indicated that parental neglect indirectly influences smartphone dependence fully mediating school adjustment. In conclusion, parental neglect indirectly influences smartphone dependence by interfering with school adjustment. In addition, reducing the negative effects of parental neglect on school adaptation may be an effective strategy to prevent smartphone dependence in adolescence.