The current observational study investigated differences in cognition, mood and appetite on days of exercise compared to rest in an active female population. It also assessed the effect of breakfast size prior to exercise on these parameters. Forty five, healthy, active females participated in the study (mean±SD age and Body Mass Index (BMI) were 21.4±3.3y and 21.8±2.8kg/m respectively) each completing a two study days in a randomized cross-over design. On each study day participants completed cognitive tasks and mood and appetite scales on a mobile phone upon waking, at 1130hrs, 1500hrs and 2000hrs. On the exercise study day they undertook a morning exercise session which was of typical mode and intensity for them. On the rest study day they refrained from any strenuous physical activity. Participants were required to keep a record of their food intake throughout the day. There were no significant differences between days of exercise and rest for cognitive task performance, appetite or energy intake. Participants were more alert on the exercise day, but more relaxed and reported better overall mood on the rest day. An increase in the kcal content of breakfast was associated with lower mental fatigue and better overall mood after exercise. In an active female population, consuming breakfast prior to exercise may improve post-exercise mood, and this effect may be dose-dependent.