Background: There is interest in the application of behavioral interventions for increasing physical activity among adults with multiple sclerosis (MS) to manage fatigue, a prevalent symptom. To date, researchers have applied social-cognitive theory (SCT) for identifying correlates of physical activity that can then inform the design and delivery of theory-based behavioral interventions. However, this research often has been conducted in heterogeneous samples of persons with and without fatigue. Behavioral interventions that focus on increasing physical activity do not specifically target persons with fatigue. This supports the examination of SCT variables as correlates of physical activity among adults with MS with fatigue and without fatigue. Objectives: This study examined SCT variables (i.e., self-efficacy, barriers, outcome expectations, goal-setting, planning, social support, and functional limitations) as correlates of physical activity in persons with MS who were fatigued and not fatigued. Methods: Persons with MS (n=189) completed self-report measures of SCT variables and wore an Actigraph GT3X accelerometer on a belt around the waist for 7 days. The accelerometer data were processed and delineated into time spent in light (LPA) and moderate-to-vigorous (MVPA) physical activity. Using Spearman rank-order bivariate correlations, we examined SCT variables as correlates of LPA and MVPA within two groups of fatigued and non-fatigued based on the cut-off score of the Fatigue Severity Scale. Results: In the overall sample, social support (rs=.154) was associated with LPA, whereas self-efficacy (rs=.383), barriers (rs=.251), and goal-setting (rs=.214) were associated with MVPA. In persons with MS who were non-fatigued, no SCT variables were associated with LPA; however, self-efficacy (rs=.392) was strongly associated with MVPA. Regarding fatigued individuals, social support was associated with LPA (rs=.239), and self-efficacy (rs=.308) and goal-setting (rs=.248) were associated with MVPA. Of note, although there was no statistically significant association, there was a trend, in that barriers may still be an important variable for increasing MVPA in fatigued (rs=.175) and non-fatigued (rs=.210) individuals. Conclusions: Self-efficacy, goal-setting, social support, and barriers may be important targets of SCT-based behavioral interventions for increasing physical activity among persons with MS, particularly persons who have severe fatigue.