--- - |2 Abstract We examined cross‐informant agreement of unsociability and associations of unsociability with social and school adjustment. Participants were 229 (48% girls; Mage = 14.25, SD = .78 years) seventh‐ and eighth‐graders in Liaoning, China. Unsociability and shyness were assessed with self‐reports and peer nominations. Social and school adjustment data were obtained from multiple sources (self‐, peer‐, teacher‐reports). Peer‐reported unsociability was not significantly correlated with self‐reported unsociability, but was positively correlated with self‐reported shyness. Path models indicated that controlling for shyness and demographic covariates, peer‐, but not self‐reported, unsociability was associated with low peer acceptance, high peer rejection and exclusion, low school liking, and low academic performance and achievement. The findings suggest that unsociable Chinese adolescents may have multifaceted adjustment difficulties with peers and at school, but only when perceived as unsociable by peers. Methodological and theoretical implications of the results and the lack of correspondence between self‐ and peer‐reports were discussed. - Social Development, Volume 27, Issue 3, Page 555-570, August 2018.