Through childhood and adolescence, youngsters are learning how to express and regulate their myriad feelings and understand the emotions of self and others. They are acquiring emotional competence. Specifically, emotional competence is the ability to purposefully and fully experience and express a variety of emotions, regulate emotional expressiveness and experience when necessary, and understand the emotions of self and others. These skills, as they develop through childhood and adolescence, support successful resolution of developmental tasks centering upon social and academic success. Based on the nature and importance of children’s and youth’s emotional competence, this chapter’s structure is as follows. First, each component of emotional competence is discussed in turn; for each, its nature and development during each age period are discussed. Second, within each component and at each age level, evidence of relations with social competence (or lack of social competence as evidenced in behavior problems) and school success (where available) are detailed. Third, components of emotional competence also may work synergistically together to promote positive outcomes; this possibility is discussed next. Fourth, others’ promotion of these competencies will be considered. Parents’ and friends’ contributions to the development of emotional competence are discussed, along with the small literature on teachers’ socialization of emotional competence. Finally, conclusions and calls for future work sum up findings and issues put forward in the chapter.