Occupational health nurses motivate employees to engage in healthy behaviors. Both clinicians and researchers need strong theories on which to base decisions for health programs (e.g., healthy diet) and experimental interventions (e.g., workplace walking). The self-determination theory could be useful as it includes concepts of individual autonomy, competence to perform healthy behaviors, and relationships as predictors of health behaviors and outcomes. In this article, the self-determination theory is described and evaluated using Walker and Avant’s criteria. The theory is applied to a population of federal employees who smoke. By increasing employees’ ability to autonomously choose smoking cessation programs, support their competence to stop smoking, and improve their relationships with both others who smoke and employee health services, smoking cessation should increase.