This study illustrates an integrative psychometric framework to investigate two sources of construct-relevant multidimensionality in answers to the Self-Perception Profile for Children (SPPC). Using a sample of 2,353 German students attending Grades 3 to 6, we contrasted: (a) first-order versus hierarchical and bifactor models to investigate construct-relevant multidimensionality related to the hierarchical nature of multidimensional self-conceptions and (b) confirmatory factor analyses (CFA) and exploratory structural equation models (ESEM) to investigate construct-relevant multidimensionality related to the assessment of conceptually related constructs. The bifactor-ESEM solution provided the best fit, suggesting the presence of both sources of construct-relevant psychometric multidimensionality. The results supported measurement invariance of the SPPC across gender and grade level and showed latent mean differences mostly supporting results from previous research.