This paper presents an exploratory-interpretive study of two multilingual adults acquiring Norwegian through extensive reading. The study examined social and cognitive aspects of language acquisition, and individual factors, such as the language learning behaviors, experiences, attitudes, and beliefs of the participants. The data were collected using background self-reports, diaries in which the participants recorded their extensive reading and related language learning experiences, and semi-structured interviews. To represent adult language learning from a multilingual perspective, the data were analyzed qualitatively using a priori themes derived from the ecological model of multilinguality (Aronin, 2016; Aronin & Ó Laoire, 2004; Aronin & Singleton, 2012). The findings suggest that environment, previous education, reasons for learning a language, and previous knowledge of other languages affect how multilingual learners approach language learning and how they use a new language.