Academic self-concept is consistently proven to be multidimensional rather than unidimensional as it is domain specific in nature. However, each specific self-concept domain may be further separated into competence and affect components. This study examines the twofold multidimensionality of academic self-concept (i.e., its domain specificity and competence-affect distinction) and extends previous research by applying both within-network and between-network approaches to construct validation. The academic self-concept scales of a German version of the Self Description Questionnaire I (SDQ I) were administered to students from 3rd to 6th grades (N = 1,958). Confirmatory factor analysis models positing separate factors for competence and affect components of math, German, and general school self-concepts fitted better than models assuming domain specificity only. This was demonstrated for the total sample as well as for different subsamples based on age and gender. Although the competence and affect components within each academic self-concept domain were substantially correlated, they were found to be separable constructs. In between-network studies, the competence component was found to be more highly correlated with achievement than the affect component within and across matching academic domains, providing a new argument for the separation of competence and affect components of academic self-concept. Implications of the distinctiveness of competence and affect components of academic self-concept for self-concept theory, research, and practice are discussed. (Contains 5 tables.)