This study explored the role of the classroom teacher in peers' evaluations of liking and disliking of their classmates. Teacher cognitions about children (teacher liking of students, teacher attributions for aggressive student behavior) and teacher behavior toward children (positive, corrective/negative) were examined as mediators in the link between children's own behavior (aggression, prosocial behavior) and peer liking and disliking. Participants were 127 second-graders in 12 classrooms (64 males, 63 females). Data on child behavior were collected through peer and teacher report, data on teacher cognitions about children were collected through self report, data on teacher behavior toward children were collected through naturalistic classroom observations, and data on peer liking and disliking were collected through peer nominations. Data were analyzed using path analysis. Results indicated that teacher cognitions about children and corrective/negative teacher behavior toward children mediated the relations between aggressive and prosocial child behavior and peer disliking.