Sarcopenia, one of the extracardiac factors for reduced functional capacity and poor outcome in heart failure (HF), may act differently between HF with preserved ejection fraction (HFpEF) and HF with reduced ejection fraction (HFrEF). We sought to investigate the impact of sarcopenia on mortality in HFpEF and HFrEF. We performed a post hoc analysis of a multicentre prospective cohort study, including 942 consecutive older (age ≥65 years) hospitalized patients: 475 with HFpEF (ejection fraction ≥45%, age 81 ± 7 years, 48.8% men) and 467 with HFrEF (ejection fraction <45%, age 78 ± 8 years, 68.1% men). Sarcopenia was diagnosed according to the international criteria incorporating muscle strength (handgrip strength), physical performance (gait speed), and skeletal muscle mass (appendicular skeletal mass). The HFpEF group consisted of fewer patients with low appendicular skeletal muscle mass index measured using bioelectrical impedance analysis [<7.0 kg/m² (men) and <5.7 (women); 22.1% vs. 31.0%, P = 0.003], and more patients with low handgrip strength [<26 kg (men) and <18 (women); 67.8% vs. 55.5%, P < 0.001], and slow gait speed [<0.8 m/s (both sexes); 54.5% vs. 41.1%, P < 0.001] than the HFrEF group, resulting in a similar sarcopenia prevalence in the two groups (18.1% vs. 21.6%, P = 0.191). Sarcopenia was an independent predictor of 1-year mortality in both HFpEF and HFrEF [hazard ratio (95% confidence interval) 2.42 (1.36–4.32), P = 0.003 in HFpEF and 2.02 (1.08–3.75), P = 0.027 in HFrEF; P for interaction = 0.666] after adjustment for other predictors. In older patients with HF, sarcopenia contributes to mortality similarly in HFpEF and HFrEF.