The purpose of this study was to examine the mediating effects of mentalization and self-system damage in the relationship between childhood trauma and relationship addiction. A survey was administered to 240 university students aged 18 to 29, and a total of 213 valid responses were used for the analysis. First, all major variables were significantly correlated. Childhood trauma, self-system damage, and relationship addiction were positively associated with each other, while mentalization was negatively associated with these variables, consistent with theoretical expectations. Second, mentalization was found to mediate the relationship between childhood trauma and relationship addiction. Third, self-system damage also mediated the relationship between childhood trauma and relationship addiction. Fourth, the sequential mediating effect of mentalization and self-system damage in the relationship between childhood trauma and relationship addiction was statistically significant. Based on these results, implications for counseling interventions for university students experiencing relationship addiction are discussed, along with limitations of the study and recommendations for future research.