The lack of behavioral interventions that aim to increase physical activity (PA) among individuals with fatigue prompted researchers to examine variables of social cognitive theory (SCT) as correlates of PA among adult patients with MS who did and did not have fatigue. The study team examined SCT variables—including self-efficacy, barriers, outcome expectations, goal-setting, planning, social support, and functional limitations—in 189 patients with MS and assessed the variables as correlates of light PA (LPA) and moderate-to-vigorous PA (MVPA) in two groups of fatigued and non-fatigued patients according to a cutoff score on the Fatigue Severity Scale. In the full cohort, social support (rs=0.154) correlated with LPA, whereas self-efficacy (rs=0.383), barriers (rs=0.251), and goal-setting (rs=0.214) were tied to MVPA. In non-fatigued persons, no SCT variables were related to LPA, but self-efficacy (rs=0.392) was strongly tied to MVPA. Among fatigued patients, social support correlated with LPA (rs=0.239), whereas self-efficacy (rs=0.308) and goal-setting (rs=0.248) were linked with MVPA. A trend indicated that barriers may still be an important variable for increasing MVPA in fatigued (rs=0.175) and non-fatigued (rs = 0.210) individuals, though there was no statistically significant association.