Depressive symptoms and social networks may influence the relationship between physical activity and cognition. Using structural equation modeling, depressive symptoms and social networks were examined as mediators between physical activity and cognition in community-dwelling older adults (N = 122), with a range of cognitive abilities (e.g., normal, mild cognitive impairment). The model included age, physical activity, sedentary behavior, sleeping, social networks, depressive symptoms, and cognitive function. A path was observed between physical activity, depressive symptoms, and cognition; specifically, those who were more physically active experienced less depression and better cognitive functioning. No relationship between social networks and cognition was found. This model fits the data well (goodness-of-fit index = .93, adjusted goodness-of-fit index = .90, root mean square error of approximation = .06). Results suggest that physical activity may mitigate depressive symptoms, with beneficial effects on cognitive functioning in both those with and without mild cognitive impairment. Suggestions for managing depression and improving cognitive functioning are provided.