Many adolescents have difficulty regulating their impulses and become prone to externalizing problems (e.g., attention-deficit/hyperactivity disorder [ADHD], oppositional defiant disorder [ODD], and conduct disorder [CD]) and other adverse consequences. Using multi-method data from a longitudinal study of Mexican-origin youth (N ϭ 674), assessed annually from age 10 to 16, we examined the relations between effortful control and ADHD, ODD, and CD symptoms over time. Bivariate latent growth curve models showed negative correlations between the trajectories of effortful control and ADHD, ODD, and CD, indicating that steeper decreases in effortful control were related to steeper increases in ADHD, ODD, and CD symptoms. Using a novel statistical technique, the factor of curves model (FOCUS), we found that ADHD, ODD, and CD share a common “externalizing” trajectory during adolescence. Although effortful control was strongly associated with this common trajectory, it had few unique associations with the individual disorder trajectories, above and beyond their shared trajectory. When we extended the FOCUS model to include the effortful control trajectory as an indicator, we found that ADHD and ODD had strong loadings, whereas effortful control and CD had comparatively weak loadings on the shared developmental trajectory. Follow-up analyses showed that a two-factor solution, with externalizing symptom trajectories on one factor and the effortful control facet trajectories on a separate factor, was a better fit to the data than a one-factor solution. Finally, parent ASPD symptoms were related to increases in CD, but had no significant influence on effortful control, ADHD, or ODD. We discuss the implications for personality and externalizing problem development.