The purpose of this study was to determine how students' (N =348) perceptions of teachers' communication behaviors predicted the extent to which students believed they shared similar group-based categorizations with their teachers and how, if at all, these beliefs impacted instructional outcomes. This study was grounded in Social Identity Theory, the Common Ingroup Identity model, and Communication Accommodation Theory, which provided a foundation to examine the intergroup relations at work within the instructional context. Through structural equation modeling attitude homophily, background homophily, and global shared social identity and teacher credibility were examined as potential mediators between teacher communication behaviors (e.g., clarity, relevance, self-disclosure, confirmation, accommodation, and nonverbal immediacy) and instructional communication outcomes (e.g., learner empowerment, in-class participation, affective learning, students' relational satisfaction, communication satisfaction, affect for teacher). In terms of teacher credibility, results indicated that teacher credibility was positively associated with learner empowerment and affective learning. Teacher clarity and confirmation behaviors positively predicted perceptions of teacher credibility, while teacher self-disclosure negatively predicted teacher credibility. In terms of teacher communication behaviors, content relevance positively predicted students' perceptions of background homophily and global shared social identity, but self-disclosure negatively predicted perceptions of background homophily and global shared social identity. In terms of mediation, teacher credibility mediated the relationship among teacher clarity and confirmation to learner empowerment and affective learning. Finally, students' identity salience moderated the relationship between perceived attitude homophily and in-class participation. Thus, when students reported higher levels of identity salience they perceived to be more similar to their teachers in terms of their attitudes, which lead to more in-class participation. These results indicated that learning outcomes are influenced more so by teacher credibility and teacher communication behaviors than group-based categorizations. This study points a continued need to explore intergroup communication and theorizing in the instructional context. This dissertation concludes with a discussion of the theoretical and practical implications from these findings for teachers, students, researchers, and administrators. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://www.proquest.com/en-US/products/dissertations/individuals.shtml.]