Research on changes in teachers' subjective theories is relevant considering that several authors have conducted descriptive analyses of teachers' beliefs, but without examining their dynamism. This study was of qualitative nature and sought to describe, interpret, and contrast the subjective theories of two teachers teaching students with Down syndrome for first time. A descriptive and interpretative analysis was conducted using Atlas.ti 7.0. The results showed that the subjective theories of both teachers on their perceptions of Down syndrome, work support, pedagogical strategies, and perceived difficulties went through similar changes. However, their subjective theories on school inclusion and students' views differed. The conclusions highlight the changes observed on the teachers' subjective theories including their interpretations of the difficulties attributed to students with Down syndrome.