Obesity was classified by BMI according to the World Health Organization: Underweight (BMI <18.5 kg/m 2 ), Normal (18.5-24.9 kg/m 2 ), Overweight (25.0-29.9 kg/m 2 ), Class I Obesity (30.0-34.9 kg/m 2 ), Class II Obesity (35.0-39.9 kg/m 2 ), and Morbid Obesity (≥40.0 kg/m 2 ). The primary outcome was 30-day all-cause readmission to any hospital after a HF admission. Mortality was assessed using the CMS Inpatient Quality Report on HF 30day mortality. Readmission reasons were classified by primary discharge diagnosis using Clinical Classification Software from the AHRQ. Results: The cohort BMI distribution consisted of 2.9% Underweight, 29.1% Normal, 30.3% Overweight, 19.7% Class I Obesity, 9.5% Class II Obesity, and 8.5% Morbid Obesity. Compared to Normal BMIs, those in elevated BMI groups were younger (P < .001) and had a higher prevalence of diabetes (P < .0001) and obstructive sleep apnea (P < .0001). The cohort's 30-day all cause readmission rate was 21.3 % (n = 309) and 30-day mortality rate was 7.1% (n = 103). Compared to the 30-day all cause readmission rate in the Normal BMI group (16.8%), readmissions were more frequent among the Overweight (22.4%; P = .04), Class I Obesity (26.8%, P = .001), Class II Obesity (24.6%, P = .04), but not Morbid Obesity (18.7%, P = .6). Mortality rates were lower among the Overweight (6.1%; P = .04), Class I Obesity (5.2%, P = .02), Class II Obesity (3.6%, P = .02), but not Morbid Obesity (6.5%, P = .2) compared to the Normal BMI group (9.9%). Of the 309 readmissions, the most frequent reasons were HF (n = 107; 35%), infection (n = 32; 10%), and AKI (n = 25; 9%). The percentage of readmissions from non-HF diagnoses were similar across BMI groups: Normal (66%), Overweight (63%), Class I Obesity (62%), Class II Obesity (68%), except Morbid Obesity (83%). Conclusions: In contrast to paradoxical effects on mortality, elevated BMI increased the rate of hospitalization after a HF admission compared to a normal BMI, except in the morbidly obese.