The present study examined the effect of mobile assisted language learning (MALL) on Iranian EFL learners' idiom learning and perceptions of classroom activities. To do so, this study was carried out in six classes at Imam Reza International University in Mashhad, Iran. The participants included 114 BA students of Teaching English field. The present study was quasi-experimental that utilized a mixed methods research design. It contained a control group with 45 participants and an experimental group with 69 participants. MALL for teaching idioms via Telegram was considered as a treatment in experimental group. In the present study, Telegram app was chosen because the researcher, the teachers, and the participants had similar experience of using this app. Pictures, texts, audio, and video files, were used as the materials in teaching idioms. Students’ Perceptions of Classroom Activities scale designed and validated by Gentry and Gable (2001) and translated into Persian and validated by Ghanizadeh and Jahedizadeh (2015) was used for assessing students’ perceptions of classroom activities (interest, choice, joy, and challenge). Twelve students in experimental group sat for an interview which was audio and video recorded. In the interview sessions, students were asked about the experience of informal learning in this research, the materials used, pros and cons toward the channel and MALL. The results demonstrated the effectiveness of mobile phone usage in enhancing EFL university students’ idiom learning as well as in students’ perceptions of classroom activities with the highest differences observed in challenge and joy perceptions. The results of the qualitative phase were also in line with those of the quantitate phase.
