Mobile Instant Messaging (MIM) applications have come into focus as potential tools to improve English language instruction, and teachers can engage more students from different backgrounds in English as a Foreign Language (EFL) classes thanks to MIM apps' distinctive features, like WhatsApp. Most of the reported studies on the use of WhatsApp in the teaching of foreign languages were performed in university or adult learning environments. The present study explores how social and emotional engagement manifest themselves in a popular instant messaging application group (WhatsApp) used by teenagers learning EFL. A focus group, a Likert scale survey, and a transcript of the WhatsApp chat were the three main sources from which data was gathered. Members' interaction records were retrieved and inductive thematic analysis was used to examine them. These findings suggest that WhatsApp provided communicative opportunities to all students, including those who did not fully engage. However, further research with a larger number of students in different contexts is necessary. [For the complete volume, "Intelligent CALL, Granular Systems and Learner Data: Short Papers from EUROCALL 2022 (30th, Reykjavik, Iceland, August 17-19, 2022)," see ED624779.]