Research Impact: Professional learning communities (PLCs), in various forms, as a venue for teachers’ professional development (PD) and learning have been the subject of increasing interest over the last decade. Yet, little is known about how social media-based PLCs might impact teacher learning. In this paper, we investigate the nature of a Twitter-based PLC. Specifically we were interested in what characteristics served to develop learning and practice. We argue that the Twitter-based PLC represented an established group of learners with varied types and levels of engagement in the Twitter conversations. These teacher differences resulted in variances in how learning was facilitated and structured. In the end, we conclude that social media can act as PD; but not without challenges.