The purpose of this study was to develop a theory of students’ transition to college and to confirm that theory. To understand the nature and meaning of the first-year transition, a qualitative study was conducted using grounded theory, and a questionnaire was developed based on the established transition theory. The validation of the theory was analyzed through structural equation modeling (SEM), and a multi-group analysis was conducted to find out what differences existed in the structural model for dormitory, self-catering, and commuting to school. As a result of the qualitative study, 112 concepts, 34 subcategories, and 9 categories were derived from open coding. As a result of the quantitative analysis through SEM, first, the higher the expectation and confidence in college, the better the transition and the greater the satisfaction. Second, the better the first-year students did at self-management, the better they transitioned, and the more satisfied they were with the transition and college. Third, transition and satisfaction with transition played a role as mediating variables between expectations and confidence, as well as between self-management and satisfaction with college, and this resulted in a sequential double mediating effect. Fourth, in the multi-group analysis, there was only one significant difference in the effect of satisfaction with transition on satisfaction with college, and that was between the self-catering and commuting groups. Based on these results, implications for educational policies for student transition and adaptation to college are discussed.