The purpose of this qualitative case study was to explore principals' perceived self-efficacy after their completion of a professional leadership cohort. Six principals from the Central Southwest region of the United States participated in this study. Each of the principals had previously graduated from a professional leadership cohort that emphasized collaborative leadership, collective efficacy, school climate and culture, and change management. Each participant of the cohort was assigned a retired veteran principal as a coach for the duration of the program. The research was conducted through the lens of Bandura's (1977) Self-Efficacy Theory with a focus on the influence of enactive mastery, vicarious mastery, verbal persuasion, and physiological arousal on the principals' perceived self-efficacy. Data for the study were collected using supplemental surveys for demographic information, interviews, observations, documents, and the Principal Efficacy Beliefs for Instructional Leadership (PEBIL) Survey (Goddard et al., 2020). Findings indicate that the professional leadership cohort, the collaborative networks developed among the cohort participants, and the coaching component of the cohort led to the principals reporting an increase in their perceived self-efficacy. The principals attributed an increase in their self-efficacy to the improved support of the teachers in their schools through classroom observations with relevant feedback, the implementation of collaborative decision-making teams including teachers, and the development of schoolwide programs. The principals shared the belief that this development of highly effective teachers in a collaborative environment with a positive school culture and climate will lead to improved student outcomes. Recommendations for future research are shared. [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://bibliotheek.ehb.be:2222/en-US/products/dissertations/individuals.shtml.]