An increasing number of adults learn more than one foreign language simultaneously. While the cognitive benefits of using multiple languages from birth have been studied extensively, little is known about possible cognitive benefits of learning multiple languages simultaneously in adulthood. Among the cognitive abilities which play a role in language learning, language aptitude (LA) and working memory (WM) are argued to be crucial. Traditionally considered relatively stable, recently they are advocated to be changeable. For example, one could imagine that learning new sounds, words, and structures in a language might both enhance the ability to temporarily hold and manage information (WM) and improve the ease with which subsequent languages are learnt (LA). Therefore, this study investigates whether LA and WM change while learning languages, and whether language learning intensity, i.e. learning one versus two foreign languages simultaneously, modulates this effect. Participants consisted of first-year and second-year Chinese university students majoring in English or English & Japanese/Russian. Data were collected twice with an interval of one academic year. The results show that all learners improved in certain aspects of LA and WM, and that among the first-year students, the two-foreign-languages learners outperformed their counterparts in WM improvement. The implications are discussed.