This article explores the complex relationship between language and mathematics education in multilingual settings by presenting an analysis of one lesson from a multilingual primary mathematics classroom in South Africa taught by an appropriately qualified and experienced teacher. English emerged as a dominant language in this classroom, and this dominance was accompanied by procedural mathematics discourse. The learners' home language functioned mainly as the language of solidarity, whereas English functioned as the language of mathematics, authority, and assessment. The article argues for the need to recognize and acknowledge the political role of language when conducting research into the relationship between language and mathematics education in multilingual classrooms. The article draws implications for making critical, influential decisions about curriculum, assessment, and teacher education. (Contains 2 figures.)