The research reported in this investigation sought to examine the self-esteem hypothesis (SEH) using measures of domain-specific and public collective self-esteem (CSE). Two studies were conducted. Each tested both propositions of the SEH The first study revealed that minimal group members (a) experienced an increase in that domain of self-esteem judged to be relatively more important to the in-group, following the display of in-group favouritism and (b) that minimal group members with low public CSE (and who thus believed that the in-group was negatively evaluated by the out-group) showed enhanced levels of in-group favouritism. The second study, which utilized the members of real social categories (i.e. New Zealanders and Australians) and negative outcome allocations (i.e. white noise) revealed identical findings. The theoretical implications of these results are discussed.