Aims: Although body mass index (BMI) is the most commonly used anthropometric measure to assess adiposity, alternative indices such as the waist-to-height ratio may better reflect the location and amount of ectopic fat as well as the weight of the skeleton. Methods and results: The prognostic value of several alternative anthropometric measures was compared with that of BMI in 1116 patients with non-ischaemic heart failure with reduced ejection fraction (HFrEF) enrolled in DANISH. The association between anthropometric measures and all-cause death was adjusted for prognostic variables, including natriuretic peptides. Median follow-up was 9.5 years (25th–75th percentile, 7.9–10.9). Compared to patients with a BMI 18.5–24.9 kg/m² (n = 363), those with a BMI ≥25 kg/m² had a higher risk of all-cause and cardiovascular death, although this association was only statistically significant for a BMI ≥35 kg/m² (n = 91) (all-cause death: hazard ratio [HR] 1.78, 95% confidence interval [CI] 1.28–2.48; cardiovascular death: HR 2.46, 95% CI 1.69–3.58). Compared to a BMI 18.5–24.9 kg/m², a BMI <18.5 kg/m² (n = 24) was associated with a numerically, but not a significantly, higher risk of all-cause and cardiovascular death. Greater waist-to-height ratio (as an exemplar of indices not incorporating weight) was also associated with a higher risk of all-cause and cardiovascular death (HR for the highest vs. the lowest quintile: all-cause death: HR 2.11, 95% CI 1.53–2.92; cardiovascular death: HR 2.17, 95% CI 1.49–3.15). Conclusion: In patients with non-ischaemic HFrEF, there was a clear association between greater adiposity and higher long-term mortality. Clinical Trial Registration: ClinicalTrials.gov NCT00542945.