The first two years of college are crucial for student retention, yet universities typically allocate significant resources to support first-year students while providing less assistance to second-year students. Second-year students face unique challenges that differ from those encountered in their first year. Previous studies examining the experiences of second-year students have revealed an increased vulnerability to dissatisfaction and dropout rates. In order to adapt successfully, secondyear students need to develop assertiveness skills. This research aims to investigate the relationship between assertiveness and adjustment among second-year students at Satya Wacana Christian University (SWCU), specifically within the Psychology Faculty. The study included 264 participants (mean age = 19.23 years, SD = 0.85 years, 71.97% female). Two measurement instruments, the Assertiveness Formative Questionnaire and the Students' Adjustment to College Questionnaire, were utilized. The correlation test results indicate a significant positive relationship between assertiveness and academic adjustment (r = 0.381, sig. = 0.000), social adjustment (rs = 0.438, sig. = 0.000), personal-emotional adjustment (r = 0.207, sig. = 0.001), and institutional attachment (rs = 0.249, sig. = 0.000). These findings suggest that higher levels of assertiveness among students are associated with greater levels of academic adjustment, social adjustment, personal-emotional adjustment, and institutional attachment. These insights can serve as a reference for other institutions to develop targeted programs aimed at enhancing students' assertiveness to facilitate the adjustment process.