This case study dissertation investigated the perceptions of mentor teachers in regard to their professional practice, teacher leadership, and workplace satisfaction. The researcher investigated the lived experiences of these teachers within the bounds of their prescribed relationships with a beginning teacher. This dissertation is motivated by three research questions: (1) What themes emerged as relevant in the professional practice of mentor teachers as evidenced by qualitative coding methods; (2) How did being a mentor cause teachers to critically examine their practice; and (3) What did the emergent themes from the research demonstrate about the impact of mentoring on the mentor teachers? Previous research on mentoring has indicated a gap in the literature in regard to the mentor teacher's experience. This model addressed how mentoring impacted the experienced teacher's career and psychosocial functions. This study evaluated how adult learning theory influenced the growth and successes of mentor teachers within this case study. The researcher conducted an in-depth case study of four mentor teachers at a rural North Carolina high school and employed a naturalistic case study methodology utilizing structured and unstructured interviews, observations, field notes, document analysis, and mentor reflections to provide qualitative data for emergent themes. The findings from the research indicated that themes of relationships, personality, art of conversation, administrative support, obstacles, helpful protocol, growth, leadership, learning from mentee, giving back, and psychosocial benefits emerged as important to the professional development of mentor teachers. The findings support modifications to this mentoring program based on adult learning theory and mentor development. [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.]