This article draws from an exploratory study of science teachers' experiences when utilising learners' home languages in teaching grade 9 learners in three South African high schools. This research investigated teacher use of learners' home languages in science instruction, with a particular focus on the affordances and challenges of using learners' home languages. The analysis of data from 15 lesson observations and 15 post lesson teacher interviews yielded four main themes. Themes one and two highlighted the affordances of integrating learners' home language with the language of instruction. These two themes were that teachers drew on learners' home language as a tool in facilitating conceptual understanding, and that through code switching, learners acquired confidence to critically express their views on science issues. Collectively, the third and fourth themes revealed limitations in this practice as teachers experienced pedagogical difficulties when invoking learners' home languages in science instruction. The third theme revealed that teachers had limited vocabulary of African language for scientific concepts, and this limited translation between English and learners' vernacular language. The fourth theme highlighted that learners who were accustomed to learning science through code switching struggled with test or examination tasks that require them to answer in English.