The influence of the principal on student learning is second only to classroom instruction of school-level factors (Grissom, 2020; Wahlstrom et al., 2011). A sustained, positive school climate is associated with a variety of positive outcomes such as improved student achievement, graduation rates, and teacher retention (Thapa et al., 2013). Principals may use social media to connect with stakeholders, in the interest of building community and school improvement. (Ferriter et al., 2012). The purpose of this sequential explanatory mixed-methods study was to investigate and explore public high school principals' perspectives on the use of social media to develop and promote a positive school climate. This study was guided by the following research questions: 1. Are there differences in principals' use of social media platforms and the following demographics: gender, years of experience, urban/urban-ring/suburban/rural? 2. How often do principals use social media to communicate with their school communities? 3. How do principals rate social media platforms as vehicles to communicate with students specifically regarding school climate? 4. How do principals describe their experiences with social media as a tool for improving school climate? 5. What are principals' beliefs about the value of using social media to develop school climate? Phase I quantitative survey consisted of high school principals (n = 53) from three small states in the northeastern U.S. Phase II qualitative focus groups included purposefully selected participants (n = 16) from the Phase I respondents. Phase III consisted of document analysis of principals' Instagram posts. The quantitative data were analyzed using descriptive statistics. The data from Phase II and III were processed according to Creswell and Creswell's (2018) protocol. Connected findings emerged: principals' communication via social media may help to build engagement with the community; principals use social media to build relationships and promote equity; and principals' posting of desired behaviors and mindsets models the expectation for the community. As a result of this study, districts should ensure social media is used consistently by principals. A predictable schedule of engaging content focused on highlighting those students typically less engaged and promoting the schools' core values may help improve school climate. [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.]