The Special Education Teacher (SET) shortage is a chronic and persistent problem with significant ethical and legal implications for school leaders. This problem is largely attributed to high rates of attrition within the field, and jeopardizes equitable learning for students with disabilities, increases costs for schools, and creates vulnerabilities to litigation. The working conditions experienced by SETs, which include personal relationships with principals, caseloads, workloads, school climate towards special education, professional development, induction programs, access to resources, and SET self-efficacy, are particularly influential on SET attrition. It is important to consider the role of principals in this issue because they are uniquely situated to affect nearly every aspect of SETs working conditions. This study used a sequential explanatory mixed-method design to investigate the types of principal support of SETs experienced and valued by SETs and principals. Quantitative surveying and qualitative informal conversations and semistructured interviewing were used to generate new information about SET and principal values, experiences and perceptions regarding principal support of SETs, and ultimately to develop new data about the effect of principal support on SET attrition. The quantitative results of this study confirm that four areas of principal support are important to both SETs and principals; however, SETs rated the amount of support received lower than principals rated the amount of support provided. Data collected in the qualitative phase confirmed that principals need to increase their support of SETs and become more knowledgeable about special education. The report also includes analysis of the implications of the study and recommendations for future research. [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.]