This study explores an online chat to determine how the dimensions of communities of practices (CoP) are reflected in participants' interactions on Twitter. The educational discussions, or Twitter chats, take place in an online microblogging platform. The CoP framework offers an approach to understanding the dimensions of mutual engagement, joint enterprise, and shared repertoire, which can be found in constructivist learning environments among educators (Wenger, 1998). A content analysis was conducted on a sample of archived educational Twitter chats to determine how often the attributes associated with CoP dimension(s) were present in the sampled chats. The findings from this study indicate Twitter chats exhibit elements of CoPs and benefit teacher professional development.