Student Number : 0008975N - M Ed research report - School of Education - Faculty of Humanities / This qualitative study was conducted in one school in an informal settlement, West of Johannesburg. The study explored how a grade 7 teacher promoted mathematical reasoning in multilingual mathematics class of English second language learners. The focus of the research was on how a Grade 7 mathematics teacher interacts with the learners to encourage mathematical reasoning during his teaching in a multilingual class. The study also looked at the kind of tasks the teacher used to promote mathematical reasoning and how he uses language to enable mathematical reasoning. The study was informed by a theory of learning which emphasises the importance of social interaction in the classroom where the teacher encourages learners to interact with each other to explain their thinking and to justify their answers. Data was collected through lesson and teacher interviews. The study shows the teacher focused more on developing the learners’ procedural fluency. This focus on procedural fluency was accompanied by the dominance of the use of English by the learners.