The "Self-Determination Inventory" (SDI) is a suite of tools developed to measure self-determination. The SDI: Student Report was recently validated for adolescents aged 13 to 22 with and without disabilities across diverse racial/ethnic backgrounds. A parallel, proxy report version to be completed by teachers or parents, the SDI: Parent/Teacher Report is also available; however, limited research has explored the congruence of ratings made on the self and proxy report versions. The present study utilized multi-group confirmatory factor analysis to compare ratings on the SDI made by adolescents and their teachers. Findings suggest that the same set of items can be used to measure self-determination using the "Self-Determination Inventory" across students and teachers, but that there are low correlations between self- and proxy-scores. Teacher respondents tended to report that adolescents had lower levels of self-determination, although the discrepancy between adolescent self-report and teacher proxy-report varied based on the disability status and race/ethnicity of the student. Implications for future research and practice are discussed.