One of the primary goals of graduate education is to transform students into scholars of their discipline – scholars who can engage undergraduate students’ inquiry in the discipline through teaching. The professional development of teaching assistants (TAs) in graduate programs is a form of socialization that involves learning the culture of their academic discipline. During their doctoral education, TAs learn how to talk, write, and teach like philosophers, geographers or engineers, and develop disciplinary communication competence, a form of communication competence that captures the ability of a new scholar to interact with other members of the disciplinary culture effectively. This chapter draws on the literature in doctoral education, organizational and intercultural communication, and educational development, to propose a conceptual framework for the development of Disciplinary Communication Competence (DCC). First, the chapter establishes the need for DCC and defines the concept. Second, it illustrates TA competencies in each domain of the DCC conceptual framework, and describes how TAs acquire and use DCC during their graduate career. Third, the chapter presents a research agenda for systematically investigating the development of DCC, the outcomes of the DCC learning process, and the impact of TA training programs designed to facilitate the development of DCC. Finally, the chapter argues that the effectiveness of TA training programs will be significantly increased by the inclusion of learning activities that enable TAs to develop disciplinary and interdisciplinary communication competence.