The purpose of this research is to: (a) examine the applicability of the Self-Description Questionnaire I (SDQI) for Indigenous and non-Indigenous Australian Year 5 and 6 students to identify a psychometrically sound measure of self-concept for Indigenous upper primary students, and (b) compare and contrast the structure and levels of self-concepts (SC) for these students to elucidate understandings about the nature of Indigenous students' self-concepts in comparison to those of their non-Indigenous peers. Applying a confirmatory factor analytic approach with Indigenous (n = 185) and non-Indigenous (n = 518) primary students (Years 5 and 6), the SDQI factor structure was found to be invariant across the 2 groups. All scales showed strong internal consistency and the factor structure was well defined for both sub-samples. The factor loadings and factor correlations were acceptable. Results of Multiple-Indicator-Multiple-Indicator-Cause (MIMIC) models found small but significant ethnicity effects favouring Indigenous students in Physical SC, but non-Indigenous students had higher School SC and Math SC compared to Indigenous students. Boys had higher Math SC and Physical SC compared to girls but girls had higher SCs in 5 of the 8 factors. A significant ethnicity x gender interaction effect was found for School SC indicating particularly low School SC for Indigenous boys. These results suggest that a tangible approach to improving Indigenous students' academic potential needs to involve enhancing academic self-concepts and that Indigenous boys' academic self-concepts need particular attention.