Reported mental health problems have risen dramatically among US college students over time, as has treatment for these problems. We examine the effect of state-level Medicaid expansion following the 2014 implementation of the Affordable Care Act on the diagnosis of mental health conditions, psychotropic prescription drug use, and the mental health status of a national sample of college students. We find that students from disadvantaged backgrounds are more likely to report being on public insurance after 2014 in expansion states relative to non-expansion states, while more advantaged students do not see this increase. Both diagnosis of common mental health conditions and psychotropic drug use increase following expansion for disadvantaged students relative to advantaged ones, which translates into an elimination of the pre-expansion gap in these outcomes by family background in expansion states. However, in contrast to some recent work on Medicaid expansion and mental health, we do not find that these changes are associated with improvements in self-reported mental health status. We also do not find that Medicaid expansion has affected risky health behaviors or academic outcomes.