Depressive symptoms are more common among sedentary individuals with longitudinal studies supporting inactivity as a potential risk factor for mood disturbances. Observational and experimental designs find that lack of exercise or exercise deprivation is associated with increased depressive and anxiety symptoms, fatigue, and pain. However, literature has not examined risk factors influencing mood deterioration in response to exercise deprivation. The current study tested the hypothesis that physically active individuals with high levels of cognitive vulnerability (i.e., a tendency towards negative thought content and processes when under stress) are at high risk for mood disturbance when undergoing exercise cessation. Community adults who met guidelines for recommended physical activity (N=36) were examined in a 4-week prospective, longitudinal study. Mood was assessed with the Beck Depression Inventory-Second Edition, the Beck Anxiety Inventory, and the Brief Profile of Mood States at baseline, after two weeks of maintained exercise, and after one and two weeks of exercise cessation. Cognitive vulnerability variables (i.e., dysfunctional attitudes, brooding rumination, cognitive reactivity) were assessed following the maintained exercise phase. Similar to prior studies, results indicated a main effect of time, such that depressive and anxiety symptoms increased over the exercise cessation protocol. Results additionally lend support for a vulnerability-stress model, with brooding rumination identified as a risk factor for the development of symptoms during exercise deprivation. This study suggests that individuals who engage in brooding rumination to cope with negative affect are at elevated risk for mood symptoms when ceasing their exercise routine.