Leadership is important for quality improvement in center-based early care and education (ECE) settings that serve children birth to five. However, little is known about who leaders are, what leaders do, and how leadership influences quality outcomes in center-based ECE settings. Leadership can be defined by the range of staff who participate in decision-making and quality improvement and the actions they take as leaders. The Early Care and Education Leadership Study (ExCELS), funded by the Office of Planning, Research, and Evaluation (OPRE) in the Administration for Children and Families, has three goals: (1) fill the gaps in definitions and measurement to understand how effective leadership can improve the quality of experiences for children ages birth to five in center-based ECE settings, (2) develop a measure of ECE leadership, and (3) identify actionable leadership development initiatives and methods of evaluating them. This snapshot presents the ExCELS theory of change to show what ECE leadership looks like as well as the influences on and the influences of ECE leadership.