This study tested the protective effects of self-affirmation for students who have the subjective sense that they do not belong in college. Such a feeling is not as visible as race or gender but, as a pervasive part of the students' inner world, might still be as debilitating to the students' academic performance. Among a predominantly White sample of college undergraduates, students who felt a low sense of belonging declined in grade point average (GPA) over three semesters. In contrast, students who reported low belonging, but affirmed their core values in a lab-administered self-affirmation writing activity, gained in GPA over time, with the effect of affirmation sufficiently strong to yield a main effect among the sample as a whole. The affirmation intervention mitigated—and even reversed—the decline in GPA among students with a low sense of belonging in college, providing support for self-affirmation theory's contention that affirmations of personal integrity can lessen psychological threat regardless of its source.