This paper presents a review of mobile collaborative language learning studies published in 2012-16 with the aim to improve understanding of how mobile technologies have been used to support collaborative learning among second and foreign language students. We identify affordances, general pedagogical approaches, second- and foreign-language pedagogical approaches, second language acquisition (SLA) principles and affective designs. The results indicate that affordances such as flexible use, continuity of use, timely feedback, personalisation, socialisation, self-evaluation, active participation, peer coaching, sources of inspiration outdoors and cultural authenticity have been emphasised. These affordances were found to be particularly suited to promote social constructivism, which is often sustained by game-based, task based and seamless learning. In terms of second and foreign language pedagogical approaches, the combination of individualised and collaborative learning prevails, along with task based, situated and communicative language learning, and raising orthographic awareness. Among SLA principles, negotiation of meaning and opportunities for feedback are highlighted. Affective aspects include increases in motivation, engagement and enjoyment, mutual encouragement, reduction in nervousness and embarrassment, and a few negative reports of risk of distraction, safety concerns, feelings of uncertainty and technical problems. The reviewed studies present a convincing case for the benefits of collaboration in mobile language learning.