Current approaches to workplace learning emphasize designing communities of practice that are intended to support both formal and informal knowledge acquisition. This article presents the design and research of a knowledge-based community of practice for Subaru, based on principles outlined by Scardamalia (2002) and Zhang, Scardamalia, Lamon, Messina, and Reeve (2007). The purpose of this study was to investigate the extent to which participants' interactions in the online community showed evidence of individual and collective knowledge building. We found evidence of knowledge building within online discussions in these areas: interactions around improvement of ideas, connection to workplace knowledge and practices, and building on or adopting the ideas of others. We also found significant gains in scores on an assessment of workplace customer service after participation in the online community of practice. (Contains 1 figure and 4 tables.)