Non-cognitive skills are a broad concept that includes personality traits, attributes, dispositions, social skills, attitudes, capabilities, and personal resources, independent of intellectual ability. The literature has shown that these non-cognitive skills play an important role in educational performance, labor outcomes, and social well-being throughout life. From a multidisciplinary perspective, this chapter discusses the concepts included within non-cognitive skills and how they relate to one another, as well as the challenges and innovations in their measurement. It then reviews the factors associated with their development, which include not only hereditary factors but also other important factors such as family income, parenting styles, family size, and the school and cultural environment, among others. Finally, the chapter discusses literature showing that the most cost-effective interventions for developing non-cognitive skills are those aimed at younger individuals and that involve families. Additionally, the benefits of effective interventions tend to be greater for socially vulnerable groups, making them even more important in the fight against inequality.