Five studies examined the effects of priming the secure base schema on intergroup bias. In addition, Studies 1-2 examined the effects of dispositional attachment style, Studies 2-5 examined a mood interpretation, Study 3 examined the mediating role of threat appraisal, and Studies 4-5 examined the effects of secure base priming while inducing a threat to self-esteem or cultural worldview. Secure base priming led to less negative evaluative reactions toward out-groups than positive affect and neutral control conditions. In addition, whereas the effects of secure base priming did not depend on attachment style and were not explained by mood induction, they were mediated by threat appraisal and occurred even when self-esteem or cultural worldview was threatened. The discussion emphasizes the relevance of attachment theory for understanding intergroup attitudes.