This dissertation was an explanatory sequential mixed methods study that sought to understand academic librarians’ involvement and experience in the Scholarship of Teaching and Learning (SoTL). Specifically, the researcher studied academic librarians’ teacher identity development through SoTL. Quantitative data were collected from a survey sent to the Association of College and Research Libraries Information Literacy listserv. Semi-structured interviews with seven academic instruction librarians who took part in the survey provided qualitative data that complemented and built upon the survey results. The theoretical framework, Communities of Practice, guided and supported the research. Results from the study indicated that academic instruction librarians are involved in SoTL for a variety of reasons, but primarily because they believe participation in SoTL improves their teaching. Also, the null hypothesis of if librarians engage in the Scholarship of Teaching and Learning, their identities will be the same as they were before was rejected, and the research hypothesis was accepted. Engagement in SoTL does impact academic instruction librarians’ teacher identity. After involvement in SoTL most research participants reported that their view of themselves as a teacher grew. Participation in SoTL also impacted academic instruction librarians’ instructional practices. After participation in SoTL, study participants reported an increase in their attitude toward self-improvement and in their use of active learning strategies. These study findings have implications for Library and Information Science (LIS) graduate schools, academic library administrations, and professional development organizations.