Undergraduates, especially those from lower income backgrounds, may perceive their social class background as different or disadvantaged relative to that of peers and worry about negative social treatment. We hypothesized that concerns about discrimination based on one's social class (i.e., class-based rejection sensitivity or RS-class) would be damaging to undergraduates’ achievement outcomes particularly among entity theorists, who perceive their personal characteristics as fixed. We reasoned that a perceived capacity for personal growth and change, characteristic of incremental theorists, would make the pursuit of a college degree and upward mobility seem more worthwhile and attainable. We found evidence across 3 studies that dispositionally held and experimentally primed entity (vs. incremental) beliefs predicted college academic performance as a function of RS-class. Studies 1a and 1b documented that high levels of both entity beliefs and RS-class predicted lower self-reported and official grades, respectively, among undergraduates from socioeconomically diverse backgrounds. In Study 2, high entity beliefs and RS-class at matriculation predicted decreased year-end official grades among lower class Latino students. Study 3 established the causal relationship of entity (vs. incremental) beliefs on academic test performance as a function of RS-class. We observed worse test performance with higher RS-class levels following an entity (vs. incremental) prime, an effect driven by lower income students. Findings from a 4th study suggest that entity theorists with RS-class concerns tend to believe less in upward mobility and, following academic setbacks, are prone to personal attributions of failure, as well as hopelessness. Implications for education and intervention are discussed.