Taking a communication approach to expertise, this study examined emergence of expertise through communication accommodation (CA) in 46 four-person face-to-face (FtF) and text-based computer-mediated communication (CMC) groups. We found that FtF members with a lower pre-discussion task confidence accommodated to the linguistic styles of those with a higher pre-discussion task confidence. Meanwhile, CA influenced post-discussion expertise judgment in CMC groups such that members who accommodated to others were judged as having less expertise. CA also influenced post-discussion expertise judgment in FtF groups after taking into account perceived task-oriented communication and perceived influence. The findings emphasize the important roles of CA and of communication channel in expertise emergence.