The importance of leadership for key educational outcomes is well documented, yet leaders’ working conditions and well-being have received considerably less attention, particularly in the early care and education (ECE) sector. Job-Demands-Resources (JD-R) theory was used to develop a holistic conceptualization of leader well-being for the purpose of examining the associations among various job demands, resources, and well-being (i.e., physical, psychological, and professional well-being) for leaders of birth to 12th grade (B–12). We tested our conceptual model via structural equation modeling (SEM) with over 2,000 ECE and K–12 building leaders across the United States. We found substantially stronger effects between job demands and well-being relative to job resources and well-being, though resources were found to be directly associated with professional well-being. Further, our tested model was similar for both ECE and K–12 leaders. Overall findings suggest that a reduction in demands—not just increased resources—is needed to ensure improved leader well-being. (author abstract)