Purpose. Time demands faced by school principals make principals’ work increasingly difficult. Research outside education suggests that effective time management skills may help principals meet job demands, reduce job stress, and improve their performance. This study investigates these hypotheses. Design. We administered a time management inventory to nearly 300 principals in Miami-Dade County Public Schools, the fourth-largest school district in the U.S. We analyzed scores on the inventory descriptively and used them to predict time-use data collected via in-person observations, a survey-based measure of job stress, and measures of perceived job effectiveness obtained from assistant principals and teachers in the school. Findings. Principals with better time management skills allocate more time in classrooms and managing instruction in their schools but spend less time on interpersonal relationship-building. Perhaps as a result of this tradeoff, we find that associations between principal time management skills and subjective assessments of principal performance are mixed. We find strong evidence, however, that time management skills are associated with lower principal job stress. Practical implications. Findings suggest that building principals’ time management capacities may be a worthwhile strategy for increasing time on high-priority tasks and reducing stress. Originality. This study is the first to empirically examine time management among school principals and link time management to key principal outcomes using large-scale data.