"Undermatched" is the name education researchers have given to the surprisingly large number of students who attend post-secondary institutions which are less selective than their academic credentials would permit, or who simply fail to even apply for college when they are qualified to do so. At first, this might seem like an obviously bad trend, especially as rates of undermatching are much higher among students from low-income backgrounds. This article argues, however, that individual cases of undermatching are sometimes morally acceptable when the choice is made autonomously. Some readers will have trouble calling this situation just, as it is one in which a disadvantaged person has decided on a course of action which will likely perpetuate this disadvantage. To address this, the article considers alternate ways in which we might distinguish between autonomous and non-autonomous choices in undermatching cases. The article concludes with some indications about how this analysis should affect future theory and policy intended to protect against unjust undermatching.