This study examined whether emotions and coping explain (mediate) the association between mother-child attachment and peer relationships. Attachment, positive and negative emotion experience, coping, and peer relationships were examined in 106 fourth-grade through sixth-grade girls attending a 6-day residential camp. Attachment, experience of positive and negative emotions, and coping were measured prior to camp with questionnaires completed by girls and their mothers. Girls reported the quality of their best friendship at camp, and camp counselors rated girls’ peer competence. Girls who perceived a more secure attachment to mother reported experiencing more positive and less negative emotions, were reported by mothers to use more social-support coping, reported more positive qualities in camp best friendships, and were rated by counselors as having enhanced peer relationships at camp. Further, the experience of positive emotions, problem-solving coping, and social-support coping mediated the links between attachment and peer relationships.