||Group recommender systems help users to find items of interest collaboratively. Support for such collaboration has been mainly provided by interfaces that visualize membership awareness, preference awareness and decision awareness. However, these mechanisms do not address group influence issues: how members may affect each other. In this paper, we investigate the roles of emotion awareness interfaces and how they may enable positive group influence. We first describe the design process behind an emotion annotation tool, which we call CoFeel. We then show that it allows users to annotate and visualize group members’ emotions in GroupFun, a group music recommender. An in-depth pilot user study with GroupFun suggests that emotion awareness features have the potential to enable group influence on preferences among group members. Most importantly, users reported CoFeel as a promising tool to annotate group recommended items in terms of accuracy and engagement. Finally, we provide design implications for emotion awareness interfaces in group recommender systems.