Objective To explore the mediating role of mobile phone dependency and self-rated health in the relationship between adverse childhood experiences (ACEs) and mental health among young adults. Methods A cross-sectional study was conducted using cluster random sampling among 1 611 young adults (mean age 26.30 years) from a region in Hainan Province. Participants completed the childhood trauma questionnaire (short form), the mobile phone addiction index, the depression-anxiety-stress scale (simplified Chinese version), and a self-rated health questionnaire. Pearson correlation analysis and mediation effect analysis were employed to examine the relationships among ACEs, mobile phone dependency, self-rated health, and mental health. Results ACEs, mobile phone dependency, and self-rated health were all significantly correlated with mental health (all P＜0.01). ACEs had a direct negative effect on mental health (direct effect＝0.221, 95% confidence interval ［CI］ 0.150- 0.293). Furthermore, ACEs exerted indirect effects on mental health through 3 pathways: the independent mediation of mobile phone dependency (indirect effect＝0.081, 95%CI 0.035-0.130), the independent mediation of self-rated health (indirect effect＝0.034, 95%CI 0.011-0.062), and the chain mediation of mobile phone dependency and self-rated health (indirect effect＝0.009, 95%CI 0.004-0.015). Conclusion ACEs have a significant impact on the mental health of young adults, with mobile phone dependency and self-rated health serving as key mediators. Interventions aimed at reducing mobile phone dependency and improving health status may help mitigate the negative impact of childhood trauma on mental health, thereby promoting psychological well-being in this population.