BackgroundTotal cholesterol is inversely associated with mortality in dialysis patients, which seems implausible in real-world clinical practice. May there be an optimal range of total cholesterol associated with a lower mortality risk? We aimed to evaluate the optimal range for peritoneal dialysis (PD) patients.MethodsWe conducted a retrospective real-world cohort study of 3565 incident PD patients from five PD centers between January 1, 2005, and May 31, 2020. Baseline variables were collected within one week before the start of PD. The associations between total cholesterol and mortality were examined using cause-specific hazard models.Results820 (23.0%) patients died, including 415 cardiovascular deaths, during the follow-up period. Restricted spline plots showed a U-curved association of total cholesterol with mortality. Compared with the reference range (4.10–4.50 mmol/L), high levels of total cholesterol (> 4.50 mmol/L) were associated with increased risks of all-cause (hazard ratio [HR] 1.35, 95% confidence index [CI] 1.08–1.67) and cardiovascular mortality (HR 1.38, 95% CI 1.09–1.87). Similarly, compared with the reference range, low levels of total cholesterol (< 4.10mmol/L) were also associated with high risks of all-cause (HR 1.62, 95% CI 1.31–1.95) and cardiovascular mortality (HR 1.72, 95% CI 1.27–2.34).ConclusionTotal cholesterol levels at the start of PD between 4.10 and 4.50 mmol/L (158.5 to 174.0 mg/dL), an optimal range, were associated with lower risks of death than higher or lower levels, resulting in a U-shaped association.Supplementary InformationThe online version contains supplementary material available at 10.1186/s12882-023-03187-1.