Three studies examined the impact of the need for cognitive closure on manifestations of in-group bias. All 3 studies found that high (vs. low) need for closure increased in-group favoritism and outgroup derogation. Specifically, Study 1 found a positive relation between need for cognitive closure and both participants' ethnic group identification and their collective self-esteem. Studies 2 and 3 found a positive relation between need for closure and participants' identification with an in-group member and their acceptance of an in-group member's beliefs and attitudes. Studies 2 and 3 also found a negative relation between need for closure and participants' identification with an out-group member and their acceptance of an out-group member's beliefs and attitudes. The implications of these findings for the epistemic function of in-groups are discussed.