This paper reports on a case study in which Twitter served as a backchannel to mediate and support the peer-teaching activity in a face-to-face, science education traditional course. Surveys and interviews were utilized to understand the effectiveness of the Twitter integration and students' perceived learning in a Twitter-supported peer teaching environment. Tweets and reflections were used to determine how pre-service teachers used Twitter to support reflection on peer instruction. Most students were able to use the Twitter platform to produce and retrieve peer feedback, while some encountered technical difficulties. Our current analysis suggests the Twitter-based peer feedback was moderately successful in this peer teaching activity. There existed a large variability of students' perceptions towards Twitter as a tool to support the delivery and reception of peer feedback.