In this chapter, we analyze the relationship between the phenomenon of adultism, as one possible factor in youth discrimination, and its effect on youth unemployment. Our review is a cross-country comparative study of Mexico, Colombia and Spain. This chapter provides explanations and analyzes differences in youth unemployment in terms of educational attainment and experience, as well as country-level economic conditions. Firms and policy makers will face the challenge of optimally managing the diverse population predicted to be active in the labor market in future years and the related challenge of avoiding ageism in the workforce.