Getting students to be physically active outside of school is a primary objective of physical educators. Teachers know that motivational tactics are instrumental and they would benefit from understanding the research that has investigated how and why individuals adopt and maintain exercise regimens. The Transtheoretical Model is one behavior-change model that has been used to identify how individuals change their physical activity behavior. Originally, this model was introduced to investigate and alter addictive behaviors, but there has been plenty of literature since that focuses on physical activity and adults, physical activity and adolescents, and how to apply it to personal training settings. Along the way, there have been worthy contributions from physical educators who wish to promote physical activity to high school students through a variety of strategies, however none of them have been supported by behavior-change research. This article identifies specific ways physical educators can apply the model in their classes.