BACKGROUND: The majority of studies suggesting that online hemodiafiltration reduces the risk of mortality compared to hemodialysis (HD) have been performed in dialysis-prevalent populations. In this report, we conducted an epidemiologic study of mortality in incident dialysis patients, comparing post-dilution online hemodiafiltration and high-flux HD, with propensity score matching (PSM) used to correct indication bias. METHODS: Our study cohort comprised 3,075 incident dialysis patients treated in 64 Spanish Fresenius Medical Care clinics between January 2009 and December 2012. The primary outcome of this study was to investigate the impact of the type of renal replacement on all-cause mortality. An analysis of cardiovascular mortality was defined as the secondary outcome. To achieve these objectives, patients were followed until December 2016. Patients were categorized as high-flux HD patients if they underwent this treatment exclusively. If >90% of their treatment was with online hemodiafiltration, then the patient was grouped to that modality. RESULTS: After PSM, a total of 1,012 patients were matched. Compared with patients on high-flux HD, those on online hemodiafiltration received a median replacement volume of 23.45 (interquartile range 21.27-25.51) L/session and manifested 24 and 33% reductions in all-cause and cardiovascular mortality (all-cause mortality hazards ratio [HR] 0.76, 95% CI 0.62-0.94 [p = 0.01]; and cardiovascular mortality HR 0.67, 95% CI 0.50-0.90 [p = 0.008]). CONCLUSIONS: This study shows that post-dilution online hemodiafiltration reduces all-cause and cardiovascular mortality compared to high-flux HD in an incident HD population.