The purpose of this study was to investigate how different forms of peer relationships offer children unique support for loneliness and to examine the direct as well as indirect effects of social behaviours and academic performance through the mediation of peer relationships on the prediction of loneliness in Korean children. Four hundred and sixty-six children were recruited from a primary school in Korea. Peer nomination, self-reports, and teacher ratings were used to measure social behaviours, peer relationships, academic performance, and loneliness. The results showed that peer relationships, including peer acceptance, the number of friends, and positive friendship quality, uniquely contributed to loneliness. Peer relationships partially mediated between withdrawal and loneliness. Peer acceptance and friendship quality fully mediated the link between academic functioning and loneliness. The findings were discussed with respect to how the social behaviours and academic performance are perceived and valued in Korean culture. (Contains 4 tables.)