The purpose of this paper is to understand student interaction and learning in microblogging-based peer feedback sessions. The researcher examined through a case study how students interacted and provided peer feedback for each other when Twitter was enabled as a backchannel; students were also asked to report how they perceived their experience. The findings suggested that students participated actively in the microblogging-based peer feedback sessions. Although Twitter supported cognitive and corrective feedback, affective feedback was dominant. Student interaction on Twitter tended to be brief and involve low-level cognitive thinking in unguided, naturalistic learning contexts. Overall, students had a positive attitude towards using Twitter for peer feedback. Problems such as distraction and information overload were also identified.