This 3-year longitudinal study investigated the prospective relationships between mobile phone dependence and mental health status (i.e., subjective well-being, anxiety and depression) and the mediating role of college adjustment among Chinese undergraduate students.The study recruited 265 first-year undergraduate students from a university (mean age = 18.95 years, SD = 0.72) in Wenzhou, China. A baseline survey and two follow-up surveys were conducted between November 2013 and December 2015 (the response rate was 76.4%). The validated Mobile Phone Addiction Tendency Scale (MPATS), Chinese College Student Adjustment Scale (CCSAS), Index of Well-being, Self-rating Anxiety Scale (SAS), and Self-rating Depression Scale (SDS) were used for assessments.The prevalence of anxiety and depression at Year 3 was 7.5% and 9.4%, respectively. Correlation analyses showed that mobile phone dependence at Year 1, college adjustment at Year 2, and mental health status at Year 3 were significantly correlated with each other. Structural equation modeling analyses showed that mobile phone dependence at Year 1 significantly predicted poor mental health status at Year 3. College adjustment at Year 2 significantly mediated the effect of mobile phone dependence at Year 1 on mental health status at Year 3.Interventions both on reduction of mobile phone dependency and improvement of college adjustment (especially among those with mobile phone dependence) are possible and needed among new college students to prevent their future depression and anxiety. Such interventions should be incorporated into regular education programs in universities.