The codevelopment of delinquent behaviors and depressive symptoms from Grade 9 to 11 was investigated on an Italian sample of 518 adolescents (399 male) after the transition to high school, evaluating the time-invariant effects of past school failure and social failure and the time-varying effects of school achievement and social problems. Bivariate latent growth model showed a positive correlation between the two intercepts and the two slopes, suggesting that during adolescence the two trajectories are reciprocally and causally related over time. Time-invariant predictors--past school failure and social failure--explain interindividual variability only for delinquent growth. Time-varying covariates--school achievement and social problems--are significantly associated with both trajectories. These time-varying variables can act as snares, mechanisms responsible for accelerating the otherwise normative pattern of increase of delinquent behaviors and actively retarding the normative decrease of depressive symptoms over adolescence. Findings highlight how interventions aimed to promote competence during adolescence can be an effective way to prevent psychopathology or to reduce its impact. (Contains 3 tables, 1 figure, and 2 footnotes.)