INTRODUCTION: Previous studies demonstrate that exercise impacts mood. Exercise training, as well as single exercise sessions, typically improves mood, although a few studies have shown a decrease in mood after exercise. The effects of different aspects of exercise, such as mode, intensity, and participant fitness have been considered. However, no study has yet examined whether including a warm-up can affect mood after exercise. Including a period of gradually increasing intensity-a warm-up- has been shown to decrease cardiorespiratory stress felt during exercise; thus including a warm-up may also alter the psychological effects of exercise. PURPOSE: To compare exercise with and without a warm-up on affect and mood measured after exercise. A secondary aim is to determine whether physiological parameters measured during exercise relate to affect and mood after exercise.Methodology: This is a secondary analysis of data collected as part of a larger project examining the effects of warm-up on several physiological and psychological outcomes. Data analyzed are from 18 physically active adults (9 women) who completed the Positive and Negative Affect Schedule and the Profile Of Mood States after two similar bouts of exercise differing with the inclusion of a warm-up. Planned analyses include a Wilcoxon sign rank test and Kendall’s Tau. SIGNIFICANCE/RAMIFICATIONS: The results of this study will add to the scientific literature about exercise and psychology. It may also suggest a means to optimize exercise sessions to improve mood.