Social difficulties and mental health are primary behavioral health concerns in autistic young adults, perhaps especially during key life transitions such as entering college. This study evaluated how dissatisfaction with social connectedness may predict and/or maintain depression and anxiety symptoms in neurodiverse, first-semester, undergraduate students (N = 263; n = 105 with diagnosed or suspected autism). Participation included a baseline survey battery, a brief survey completed twice per week across 12 weeks, and an endpoint survey battery. Social dissatisfaction at baseline was prospectively associated with biweekly ratings of depression symptoms, when controlling for baseline depressive symptoms. Social dissatisfaction was synchronously related to elevated sadness, anhedonia, and anxiety throughout the semester. These relationships were generally consistent across levels of baseline social motivation; however, there was one significant moderation effect--the negative relationship between baseline social satisfaction and anxiety was strongest for more socially motivated participants. More autistic traits were related to lower social satisfaction at baseline and greater mood concerns across timepoints. In contrast, greater autistic traits at baseline were related to greater satisfaction with social connectedness throughout the semester. Results support ongoing efforts to address mental health in autistic college students by highlighting the importance of social satisfaction.