This study extended the internal/external reference model to multiple languages including students' language of instruction, first foreign language, and second foreign language. We examined whether social and dimensional comparisons play similar roles in the formation of students' self-concept related to different languages and whether dimensional comparisons result in contrast or assimilation effects. All students had German as the language of instruction and English as the first foreign language. Students were divided into a subsample (N = 487) learning French as a second foreign language and a subsample (N = 481) learning Latin. Invariance tests demonstrated that the achievement--self-concept relations were similar across the subsamples, but interesting group differences became apparent when analyzing the French and Latin subsamples separately.