The main purpose of this study is to broaden our understanding of the predictors of self-control. We test how two types of strain variables (bullying victimization and grade dissatisfaction) influence the level of self-control during adolescence using three-wave panel data collected from Korean adolescents ranging in age from 14 to 16. We estimated two-level random effects regression models using hierarchical linear model(ing; HLM) 7.0. The results revealed that these two strain variables have negative, significant within-individual and between-individual effects on adolescent self-control. In addition, adolescents who have experienced a higher level of mean grade dissatisfaction over 3 years showed a more decreasing trajectory in the development of self-control during the same period. The result indicates that strainful circumstances can account for within-individual self-control deterioration as well as between-individual differences in the developmental trajectory of self-control.