Based upon a sample of 232 German elementary school students aged 9–12 years, the present longitudinal study aimed to examine the relations between achievement, self-concepts, and intrinsic values in music, mathematics, and verbal domains within the generalized internal/external frame of reference model (GI/E model). Results showed significantly positive achievement-self-concept/intrinsic value relations within domains and some significant achievement-self-concept/intrinsic value relations across domains: Mathematics achievement negatively predicted verbal self-concept, verbal intrinsic value, and music intrinsic value, whereas verbal achievement positively predicted music self-concept and music intrinsic value but negatively predicted mathematics intrinsic value. Music achievement, in turn, positively predicted verbal intrinsic value. All three self-concepts mediated the achievement-intrinsic value relations within domains. Furthermore, verbal self-concept proved to mediate the relation of mathematics achievement to verbal intrinsic value, whereas music self-concept also proved to mediate the relation of verbal achievement to music intrinsic value.