The present study examines the professional growth of three Chinese English teachers by analyzing their interactional patterns and their social and cognitive presence in an online community. The data from social network analysis (SNA) and content analysis revealed that computer-mediated communication (CMC) created new opportunities for teachers to interact personally, socially and professionally with other fellow teachers with whom they would otherwise not have contact in their working milieu. At the initial stage of their online communication, newcomers to the forum were more likely to rely on vertical relationships, preferring to communicate with people with more expertise or power in the community. New horizontal, peer-to-peer relationships emerged with their increasing involvement in online discussion. Moreover, codes of social presence were frequently used by the participants, especially by the peripheral members in the community. "Elucidating" was the most frequent category of cognitive presence codes used by all the participants while the codes of the other three phases varied with individual teachers. No significant change was observed in the development of cognitive presence likely due to the effect of the time variable. The study has some practical implications for the professional development of language teachers in an online community.