In this longitudinal study, we examined the effect of vocational interest profiles on the development of achievement in two core subjects in upper secondary level. Vocational interests according to Holland (1997) were modelled by individual profiles including the parameter level as well as the dimensions Things/People and Data/Ideas (Prediger, 1982). Furthermore, we included self-concept and course level in our analyses and investigated the mediating effects of interest profiles on the self-concept–achievement-relation and the course level–achievement-relation respectively. Our results revealed a positive effect of the Things/People dimension on the development of mathematics achievement. Contrary to our assumptions, we found no association between vocational interests and the development of achievement in English. We confirmed significant positive effects of self-concept and course level on the change in achievement in both subjects. Only in mathematics vocational interests turned out to mediate these effects. In sum, this study revealed subject-specific differences in the effects of vocational interest profiles on the development of achievement.