Objectives This study sought to test the moderated mediating effect by examining whether career decision-making level (CDM) plays a mediating role in the effect of self-differentiation on adjustment to college Life and whether career preparation behavior(CPB) plays a controlling role in the relationship between self-differentiation and CDM.
 Methods In order to do so, a questionnaire was distributed to male and female college students nationwide through an online survey company. A total of 351 questionnaires were analyzed and the collected data were analyzed by using SPSS 22.0 and Process Macro v4.1. First, we investigated whether CDM plays a mediating role in the relationship between college students' self-differentiation and adjustment to college Life. Next, we investigated whether CPB plays a moderating role among the three variables. Finally, the moderated mediating effect of CDM through CPB was tested.
 Results The results showed that self-differentiation, CDM, CPB, and adjustment to college Life were all positively correlated. However, the relationship between self-differentiation and CPB was not statistically significant. Self-differentiation was found to have a positive effect on adjustment to college Life through CDM, and the effect was significant even after controlling for the mediating variable. CPB was found to be a moderating factor in the relationship between self-differentiation and CDM. Finally, the interaction between self-differentiation and CPB was found to have a significant effect on CDM, and CDM was found to have a significant effect on adjustment to college Life.
 Conclusions Based on the results of this study, the implications, limitations, and suggestions for future research are presented.