Attachment theory proposes that young children's experiences with their caregivers has a tremendous influence on how children navigate their social relationships. By the end of early childhood, intergroup contexts play an important role in their social life and children build strong ties to their ingroups. Although both domains relate to the same psychological processes--children's affective ties to others--surprisingly very little research has addressed how children's attachment relates to their intergroup attitudes and behavior. In this study, we investigate the link. For that purpose, 5-year-old children (n = 100) first underwent the German Attachment Story Completion Task (GEV-B). Then we allocated children into minimal groups based on T-Shirt color and assessed their intergroup attitudes and intergroup behavior. Results showed that while most children showed a strong and robust ingroup bias in their attitudes and behavior, children with an insecure-ambivalent attachment representation treated in- and outgroup similarly. Overall, this study provides novel perspectives on the relationship between children's attachment representation and their interactions in the social world.