This article shares findings from a study conducted in the southeastern United States of the impact of a teacher leadership course on upper elementary, middle, and high school mathematics and science teachers. Fifty-nine teachers completed the course and data analysis showed growth in understanding in five areas of teacher leadership. This growth was analyzed using a four-image teacher leadership conceptual framework. Data analysis revealed a fifth image of growth that more fully represented the teacher leadership development of the participating teachers. Details of specific teacher leader characteristics within each image are included and findings are presented addressing growth within each of the five images based on the course experience. Discussion is offered about the implications for mathematics and science teacher leader development derived from the data analysis.