Self-concepts of ability (SCA) and intrinsic task values (ITV) are key determinants of students' choice of study program and dropout. Both constructs are multidimensional (i.e., specific to curricular learning content) and hierarchically structured (i.e., aggregate into one or more higher-order factors). The present study investigated German business studies students' (N = 375; age: M (SD) = 21.8 (5.51); 59% female) subfield-specific SCAs and ITVs. Longitudinal data collected at the transition into higher education (t1) and toward the end of the first semester (t2) gave insight into (changes in) interrelations and antecedents of subfield-specific SCAs and ITVs during the introductory study phase, when students likely had to review their hitherto anticipated motivational beliefs. Results from confirmatory factor analyses and structural equation modelling revealed that interrelations of SCAs and ITVs decrease over time. SCAs correlate increasingly strongly within a mathematical and a verbal domain compared to cross-domain correlations. Accordingly, mathematics, but not German SCA, from high school predicts all subfield-specific SCAs at t1, but only mathematical subfield SCAs at t2. However, the pattern of results for ITVs is less systematic. Curricular and practical implications of the subfield-specific formation of motivational beliefs at the transition into higher education are discussed.