In 2 studies, the author examined the effect of collective self-esteem (CSE; J. Crocker & R. Luhtanen, 1993) on people's willingness to display in-group favoritism. To test that self-esteem hypothesis, he measured public CSE, rather than private CSE, because the former parallels a threat to social identity, a state believed to motivate ingroup favoritism. Furthermore, the author explored whether group identification and self-stereotyping moderated the effect of public CSE on in-group favoritism. The participants were 92 British and Dutch university employees. As expected, participants high in public CSE displayed more in-group favoritism than did those low in public CSE. Moreover, group identification and self-stereotyping appeared to moderate the effect of CSE.