We investigated the link between prolonged sedentary bouts and all-cause mortality in patients on chronic hemodialysis, using a prospective cohort. A total of 104 outpatients on chronic hemodialysis from 2013 to 2019, aged 71.4±11.4 years, were enrolled. Prolonged sedentary bouts (≥ 30 min and ≥60 min) (min and bouts) and relative prolonged sedentary bouts (≥ 30 min and ≥ 60 min) (%) on the patients’ non-hemodialysis days were measured by a tri-accelerometer, and we also analyzed the patients’ clinical parameters. The relationship between prolonged sedentary bouts and all-cause mortality was evaluated by a survival analysis and the Cox proportional hazard model. Thirty-five patients died during the follow-up period. A Kaplan-Meier analysis detected significant differences in the survival rate between two groups stratified by the median for all prolonged sedentary-bout parameters. After the adjustment for confounding factors, all of the prolonged sedentary-bout parameters were determinant factors for all-cause mortality. These results indicate that prolonged sedentary bouts on non-hemodialysis days were closely related to all-cause mortality in the patients on hemodialysis.