Objective: This study examined the growth pattern in physical aggression over a five-year period among South Korean early adolescents and the effects of temperament (anger/frustration and emotion regulation) and parenting (harsh parenting and parental monitoring) on early adolescents’ physical aggression.

Design: A five-year longitudinal design was used to explore the growth pattern in physical aggression.

Method: Participants were 2844 early adolescents (1320 girls and 1524 boys; M age = 9.86 years, SD = 0.35 at wave 1) in the Korea Youth Panel Study (KYPS), a national representative of Korean children and adolescents. The latent growth curve model (LGM) was used for data analysis.

Results: There was a significant linear growth over time in physical aggression during early adolescence. However, there were significant individual differences of developmental trajectories of adolescent aggression. The initial level of aggression in early adolescence was positively associated with anger/frustration, and the rate of change in aggression was negatively related to emotion regulation. Parenting variables, which were harsh parenting and parental monitoring, were not related to the initial level and rate of change in physical aggression.

Conclusion: Temperament variables (anger/frustration, emotion regulation) cause the individual differences in initial level of aggression and rate of change in aggression.