This article reports on multilingualism in adult literacy education in Timor-Leste and explores how choices made at the formal level of national language policy are dealt with at the operational level of adult literacy education. The 2002 constitution of Timor-Leste declares Portuguese and Tetum as the official languages. It recognises the need for regional languages to be valued and developed by the state and proclaims Indonesian and English as working languages. The national language-in-education policy is mainly concerned with Portuguese and Tetum. A broad study of 100 teachers and about 750 learners, and an in-depth study in 20 classes, revealed the interplay between the official language and language-in-education policy and the country's complex multilingual setting in adult literacy education. Tetum was the target language in literacy programmes, but the (broad) study found no clear differences in beginning literacy skills (the reading and writing of words) between learners with and without proficiency in Tetum. The studies revealed the strong position of Tetum and the educational importance of regional languages, and both findings are mirrored in more recent versions of the language-in-education policy. The studies also revealed the more limited occurrence of Portuguese in both teachers' and learners' language proficiency and day-to-day use, as well as in adult literacy education.