Assessment in 2nd and foreign language learning has often centered on proficiency, although motivation has been shown to be critical in learning in general, as well as in 2nd and foreign language acquisition specifically. One of the issues relevant to the assessment of motivational processes in this area is that of cultural differences. In much of the existing work, motivational processes and constructs are assumed to be invariant across cultural and linguistic groups. This may be due to limitations in the existing models or in the narrowness of populations sampled. The purpose of this study was to test the robustness of motivational processes in language acquisition across different ethnic subgroups for the purpose of informing efforts to create more valid and sensitive measures. Participants in the study completed a background information survey, a motivation information questionnaire, and a learning outcome questionnaire. Factor analysis yielded 7 factors, and comparative analyses confirmed the importance of cultural and subgroup differences regarding motivational beliefs and suggested the importance of intragroup heterogeneity in future research and theory development. The implications for the development of broader assessment approaches are discussed.