This study investigated the facilitative role of adult social self-efficacy in Chinese college students' first-year transition. We proposed and tested a process model in which perceived social support was hypothesized as a mediator between social self-efficacy and college freshmen adjustment. Participants were 474 college freshmen enrolled at a large university located in an east coast city in the People's Republic of China. These college freshmen completed four waves of self-report surveys over a 10-month period, at 1, 4, 7, and 10 months post-entry, respectively. Participants' first-year cumulative grade point average (GPA) was obtained from the University Registrar. Results based on structural equation modeling provided support for the hypothesized process model. Specifically, social self-efficacy (Month 1) positively related to perceived social support (Month 4), which in turn positively related to academic and social adjustment, but negatively related to depression (Month 7). Perceived social support was found to mediate the above relationships. Academic adjustment positively related to, whereas depression negatively related to, first-year GPA (Month 10). The relationship between social adjustment and first-year GPA was complex, with a negative direct link and a positive indirect link through academic adjustment. In addition, academic and social adjustment positively related to subjective well-being (SWB; Month 10), whereas depression negatively related to SWB. Implications for research and practice were discussed.