The significant role of language in mathematics teaching and learning is not a new phenomenon. Given the growth of cultural and economic migration, the increasing international focus on education for economic development and the widespread use of English as a language for learning, we have become acutely aware of the importance of language in adults’ mathematics learning. While investigation has been undertaken in relation to the role of language in the learning and teaching of mathematics at primary and second level, little research has been done on multilingual (including bilingual) adults’ learning of mathematics and the ways in which teaching might support such learning. In this paper we investigate the role of language in the mathematics and numeracy education of bi/multilingual adults with a focus on the mathematics register and discourse; we address the relationship between language(s) and learning; we provide a review of available literature specific to adult learners; and discuss implications for adult mathematics education.