This paper reports on a study of the effects of Twitter-enabied mobiie communication devices on group decision-making and group dynamics. One hundred and sixty-seven university students formed 44 groups under fwo distinct communication conditions: Twitter operating on mobiie communication devices (TMCD), and Google Groups online message boards (OMB) accessed through personal computers. Each group was tracked as if completed an assigned set of group decision-making tasks. The sfudy's results are analyzed throught media synchronicity theory and its distinction between conveyance and convergence communication processes. TMCD exhibifed significantly fewer conflicting (unfriendiy) messages and a greater number of intiatory messages than OMB. Moreover, with tasks involving convergence communication processes, TMCD achieved significantly higher levels of conformity and satisfaction than OMB. These results impty that hightweight, portable mobile communication devices (MCDs), enabled with Twitter or another similar inferface, complement conventional computer-mediated communication, offering an effective means or group decision-making.