Shyness, the tendency to be inhibited and uncomfortable in novel social situations, is a consequential personality trait, especially during adolescence. The present study examined the development of shyness from late childhood (age 10) through adolescence (age 16) using data from a large, longitudinal study of Mexican-origin youth ( N = 674). Using both self- and mother-reports of shyness assessed via the Early Adolescent Temperament Questionnaire–Revised, we found moderate to high rank-order stabilities across 2-year intervals and a mean-level decrease in shyness from age 10 to 16. Anxiety and depression were associated with higher initial levels of shyness, and anxiety was associated with greater decreases in shyness from age 10 to 16. Contrary to predictions, neither nativity (country of birth) nor language proficiency (English, Spanish) was associated with the development of shyness across adolescence. Thus, youth generally decline in shyness during adolescence, although there is substantial individual variability in shyness trajectories.