Teachers face numerous challenges: feeling isolated in their classrooms, overwhelmed by the demands of the job, and disappointed in traditional professional development. Prior research has pointed to Twitter as a possible solution to these challenges, so we examined teacher participation in the hashtag space #MTBoS (the mathtwitterblogosphere). We sought to answer: Do teachers’ contributions to #MTBoS demonstrate the characteristics of participation in a community of practice (CoP)? To answer, we collected 6,985 unique tweets tagged with #MTBoS. We qualitatively coded a sample of 100 original posts to analyze the quality of content as related to four characteristics of a community of practice (CoP): (a) domain of knowledge, (b) community of people, © shared practice, and (d) discipline of convening. In this initial exploration, we found that there is evidence of #MTBoS functioning as a CoP and further research is warranted.