Abstract Aim To explore the relationship between the serum sodium level on admission and all‐cause mortality in HF patients. Design A single‐center retrospective cohort study. Methods Patients hospitalized with HF at the Heart Failure Center, Fuwai Hospital, from November 2008 to November 2018 were enrolled. Results A total of 3649 patients were included, and the mean sodium level was 137.19 ± 4.36 mmol/L, with a range from 115.6 to 160.9 mmol/L. During a median follow‐up of 1101 days, mortality occurred in 1413 (38.7%) hospital survivors. After adjustment for age, sex, and other potential confounders, patients with sodium levels