Skill mismatches are highly prevalent in today’s labour market and may cause serious costs and consequences for individuals, companies, and societies. This cumulative dissertation provides an umbrella view of skill mismatches. It addresses the core issues of skill mismatch, that is, adequate measurement, as well as the causes and consequences of individuals’ skill mismatches. The dissertation emphasizes the significance of applying the appropriate measurement method and demonstrates the crucial role of different facets of education for skill matching over the course of the career. In addition, it illustrates the implications of skill mismatches on individuals’ monetary and non-monetary labour market returns. For example, the findings show that the monetary consequences of skill mismatches can differ significantly depending on the skill domain and that individuals’ subjective perceptions of the skill mismatch situation are decisive for their subjectively perceived job quality.