The potential socialization effects of entrepreneurial work are largely underresearched. In this longitudinal study, we quantify socialization effects of self-employed work by examining the career progression in a sample of college students between their final college year (T1) and 15 years later. We focus on both changes in “dark traits” such as narcissistic and antisocial profiles and changes in an entrepreneurial personality profile (intraindividual entrepreneurial constellation of the Big Five traits). We find indications that self-employed work is indeed associated with an increase in “dark traits” in males and in the entrepreneurial profile in the total sample. We further found that job autonomy mediates the socialization effect of self-employment on the entrepreneurial personality profile.