The goals of this study were to examine children's meta-perceptions and meta-accuracy of acceptance and rejection in the peer group, the degree to which these perceptions vary by perceiver sex and sex of the reference group, and the association between these perceptions and children's actual functioning in the peer group. Participants were 644 fourth-grade children. Meta-perceptions and meta-accuracy were derived from sociometric nominations of actual and perceived acceptance and rejection. Children more accurately perceived how they were seen by same-sex peers than how they were seen by other-sex peers. They also perceived more rejection than acceptance from other-sex peers. Meta-accuracy for rejection was low regardless of the sex of the reference group. Sex of the reference group significantly moderated the association between meta-perceptions and meta-accuracy of acceptance and rejection and children's actual peer relationships. These findings indicate the importance of examining these relatively understudied social cognitions in research with children and the importance of taking the sex of the reference group into account in future peer relations studies using peer nomination methods.