This paper argues that assortative matching may explain over-education. Education determines individuals' income and, due to the presence of assortative matching, the quality of partners in personal, social and working life. Thus, an individual acquires education to improve the expected partners' quality. However, since every individual of the same level of ability acquires the same level of education, the relative levels of education among individuals do not change, the expected partners' quality does not increase and over-education emerges.