As principals seek to improve educational experiences for students, they partner with many individuals. One of their leading supporters in pursuing learning is their supervisor. In the past, principal supervisors focused on compliance. In the current landscape, principal supervisors serve as principal support and evaluators. Each working relationship is different though there are some common practices used in their work together. Through this study, I sought a clearer understanding of how principal supervisors differentiate their practices to best meet principals' professional learning needs. Through a comparative multiple case study using observation, interview, and document analysis, I explored the differentiation practices of principal supervisors when working with multiple principals. Findings confirm that principal supervisors use differentiation practices to support learning needs in four ways. Principal supervisors: (1) build partnerships, (2) use contextual information and principal needs, (3) are supportive experts, and (4) are flexible coaches. Findings from this study inform the selection of and professional learning designed for those in the principal supervisor role. Additionally, findings support the continued adoption and support of this revised role across more districts in the United States. Finally, findings suggest the need for further research into the professional learning for principal supervisors. [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.]