Research suggests people try to protect their social self-esteem from threats from the ingroup or the outgroup. However, how members react to a threat to social self-esteem from a third party remains unclear. Three studies were conducted to examine the influence of a threat to social self-esteem from an authoritative third party on ingroup favoritism. We explored the effect of negative (versus positive) evaluation from the testing system on explicit and implicit ingroup favoritism in Study 1 and Study 2 respectively. We compared the effect of negative evaluation posed by the testing system or the competitive outgroup on ingroup favoritism in Study 3. Results suggested that individuals experiencing a threat to social self-esteem from an authoritative third party manifested less ingroup favoritism than those experiencing no threat or outgroup threat. The theoretical implications of this research on social identity theory and the practical implications of reducing intergroup bias are discussed.