The purpose of this study was to investigate the mediating effect of mattering between insecure adult attachment (anxiety and avoidance) and college life adjustment. For this purpose, a questionnaire of 446 four-year university students in Seoul and Gwangju was used for statistical analysis. In this study, a questionnaire consisting of adult attachment scale, Korean version of mattering scale, and college life adjustment scale was used, and statistical analysis was conducted using SPSS 22. The results of this study are summarized as follows. First, there was a significant negative correlation between insecure adult attachment (anxiety and avoidance) and mattering as a mediator, and the relationship between mattering and college life adaptation. Second, mattering showed a partial mediating effect in the relationship between attachment anxiety and adjustment to college life adjustment. Third, in the relationship between attachment avoidance and college life adjustment mattering also showed a partial mediating effect. The suggestions were made based on the results of this study.