Across the globe, people are using smartphones to connect, communicate, and interact with other users. The sheer popularity of Mobile Instant Message (MIM) applications caught scholarly attention in exploring their potential in language learning settings. Chapter 4 investigates the efficacy of WhatsApp use in adult language learning with an aim to examine its affordances and constraints. Following a case study design, online observations and semi-structured interviews were used to elicit data for the study. Participants were adult learners of German in a community college in the UK, who were using WhatsApp over a period of 22 weeks. Chapter 4 places attention on the ways in which members of the group interact (or not) with each other by studying a succession of communicative events. The findings indicate that WhatsApp can afford synchronous (near synchronous), asynchronous, and/or diachronic communication, while its archived nature can enable learners to access previous chat entries retrospectively and decipher what other users had shared without temporal constraints. The analysis points to learners’ reactive participation and limited interaction, which is further discussed in this chapter through a selection of communicative events.