This research study explored perceived influence of an instructional coaching program on teacher self-efficacy based on voluntary participation in comparison to mandated participation. At the time of this study, the literature on instructional coaching incorporated studies that tie instructional coaching to increases in teacher self-efficacy; however, the literature only connected the two based on voluntary relationships. It was not known how teacher self-efficacy was influenced when instructional coaching relationships were mandated, in comparison to when the relationships were voluntary. The purpose of this qualitative study was to delineate the perceived impact that one school district's instructional coaching program had on teacher self-efficacy when the professional development program is voluntary, in comparison to when it is mandated. The research design method for this study was qualitative research methodology based on case studies. Data was collected from the one-on-one semi-structured interviews. The findings eluded that from the teacher perspective, instructional coaching has the ability to positively influence the self-efficacy of those who volunteered to participate in instructional coaching, as well as those who were mandated to participate in instructional coaching. Subsequent findings highlighted that instructional coaches believe that with adequate training, time, and resources, instructional coaching has the ability to positively influence all participants who participate in an instructional coaching program. The results of this study can contribute to the body of literature regarding teachers' sense of efficacy based on their experiences with instructional coaching relationships. The findings can assist district-level and school-level administrators, instructional coaches, and curriculum specialists to help sustain instructional coaching as an on-going professional development practice, and help determine how an instructional coaching program is assessed in order to meet the need and goals of all stake-holders involved in the process. [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.bibliotheek.ehb.be/en-US/products/dissertations/individuals.shtml.]