Examining the awareness of English as a Foreign Language (EFL) learners and their on-task behaviours during pair work activities in the classroom, this qualitative case study aimed to reveal the effectiveness of peer interaction in L2 learning and the factors that have an impact on the effectiveness of peer interaction in pair work tasks. The participants of the study consisted of a group of 21 adult learners in a higher education EFL context. Observations, field notes, audio-recordings of peer interaction during tasks and lastly semi-structured interviews were conducted to collect data. The findings show that the interaction in pair work activities in EFL classrooms can facilitate learning through cooperation and collaboration. In addition to this, the learners' awareness and behaviours are multidimensional since they are related to the (1) self, (2) peer and teachers, and (3) tasks. The results have implications for effective use of pair work activities in EFL classrooms.