Hospital readmissions remain a continued challenge in the care of patients with heart failure (HF). This study aims to examine the rates, temporal trends, predictors and causes of 30-day unplanned readmissions after admission with HF. Patients hospitalized with a primary or secondary diagnosis of HF in the U.S. Nationwide Readmission Database were included. We examined the incidence, trends, predictors and causes of unplanned all-cause readmissions at 30-days. A total of 2,635,673 and 8,342,383 patients were included in the analyses for primary and secondary diagnoses of HF, respectively. The 30-day unplanned readmission rate was 15.1% for primary HF and 14.6% for secondary HF. Predictors of readmission in primary HF included renal failure (OR 1.27 (1.25 to 1.28)), cancer (OR 1.26 (1.22 to 1.29)), receipt of circulatory support (OR 2.81 (1.64 to 4.81)) and discharge against medical advice (OR 2.29 (2.20 to 2.39)). In secondary HF, the major predictors were receipt of circulatory support (OR 1.43 (1.12 to 1.84)) and discharge against medical advice (OR 2.01 95%CI (1.95 to 2.07)). In primary HF 52.4% of patients were readmitted for a noncardiac cause while for secondary HF 73.9% were readmitted for a noncardiac cause. For secondary HF, the strongest predictor of readmission was discharge against medical advice (OR 2.06 95%CI 2.01 to 2.12, p < 0.001). Early unplanned readmissions are common among patients hospitalized with HF, and a majority of readmissions are due to causes other than HF. Our results highlight the need to better manage comorbidities in patients with HF.