The purpose of this study was to investigate the correlations among physical, relational aggression and friendship quality and the similarity of perceptions of friendship quality between friends. Moreover, APIM was applied to examine the actor and partner effects of aggression on friendship quality. The subjects were 339 5th grade children recruited from 2 public primary schools located in Gyeonggi province. The results demonstrated that there were significant correlations between friendship quality and both types of aggression. The perceptions of help, intimacy, emotional stability, and conflict between friends were significantly similar. Finally, there were significant self-effects of physical aggression on friendship conflict. Moreover, there were self-and partner-effects of relational aggression on friendship conflict.