This study examined patterns of delinquent behavior trajectory from late childhood to early adolescence and examined relationships between patterns of trajectory and individual, family, and school factors. Youth delinquent behavior trajectories were examined by mixed growth models using data from the 2nd to 5th year surveys of the Seoul Panel Study of Children. Relationships between patterns and effect factors were examined by multinominal logit models. Four patterns emerged: non-delinquency (80%); rapidly accelerating delinquency (3.3%); decelerating delinquency (6.0%); and moderately accelerating (10.7%) groups. Contacts with a delinquent peer group had persistent effects on more serious delinquent behavior trajectories. Increased levels of self-esteem and school achievement prevented increase in delinquent behaviors; close relationships with parents and parental supervision caused decrease in delinquent behaviors.