<i>Background:</i> Circadian variation in blood pressure (BP), which is commonly blunted among patients with chronic kidney disease (CKD), has been associated with increased cardiovascular risk. The causes of this blunted circadian variation remain incompletely understood. <i>Methods:</i> We hypothesized that physical activity is a determinant of circadian BP variation. Accordingly, we studied 101 patients with CKD (mean age 69 years, mostly men) with 24-hour ambulatory BP monitoring and simultaneous monitoring of physical activity on 2 occasions 4 weeks apart. <i>Results:</i> Measured by wrist actigraphy, a higher level of physical activity was associated with lower overall mean BP. A higher level of activity also altered the circadian systolic BP rhythm; this alteration was characterized by both a higher amplitude of variation (and thus greater dipping) and restoration of acrophase (time at peak BP) to a less vulnerable period for cardiovascular events. Among the most sedentary participants, both systolic and pulse pressure acrophases were seen in the early hours of the morning which is also the most vulnerable period for cardiovascular events. <i>Conclusion:</i> Physical activity is an independent determinant of circadian variation in BP. We speculate that among patients with CKD, a sedentary lifestyle, rather than non-dipping, mediates increased cardiovascular risk.