AIMS: Previous reports have provided conflicting data regarding the relationship between length of stay (LOS) and subsequent readmission risk among patients hospitalized for heart failure (HF). METHODS AND RESULTS: We performed a post-hoc analysis of the Efficacy of Vasopressin Antagonism in Heart Failure Outcome Study with Tolvaptan (EVEREST) trial to evaluate the differences in LOS overall and between geographic regions (North America, South America, Western Europe, and Eastern Europe) in association with all-cause and cause-specific [HF, cardiovascular (CV) non-HF, and non-CV] readmissions within 30 days of discharge after HF hospitalization. The present analysis included 4020 patients enrolled from 20 countries who were alive at discharge. Median [interquartile range (IQR)] LOS was 8 (4-11) days. The 30-day readmission rates were 15.7% [95% confidence interval (CI) 14.6-16.8] for all-cause; 5.6% (95% CI 4.9-6.3) for HF; 4.4% (95% CI 3.8-5.1) for CV non-HF; and 5.8% (95% CI 5.1-6.6) for non-CV readmissions. There was a positive correlation between LOS and all-cause readmissions (r = 0.09, 95% CI 0.06-0.12). The adjusted odds ratio for the top (≥14 days) vs. the bottom (≤3 days) quintile for LOS was 1.39 (95% CI 0. 92-2.11) for all-cause readmissions, 0.43 (95% CI 0.24-0.79) for HF, 2.99 (95% CI 1.49-6.02) for CV non-HF, and 1.72 (95% CI 1.05-2.81) for non-CV readmissions. With the exception of Western Europe, these findings remained largely consistent across geographic regions. CONCLUSION: In this large multinational cohort of hospitalized HF patients, longer LOS was associated with a higher risk for all-cause, CV non-HF, and non-CV readmissions, but a lower risk of HF readmissions within 30 days of discharge. These results may inform strategies to reduce readmissions.