The aim of this work was to investigate the predictive value of in-hospital posture and ambulatory activity for 30 days following discharge on functional status in older patients with heart failure.We undertook a prospective observational pilot study of 27 patients (78 ± 9.8 y, 51.8% female) admitted with heart failure. Participants wore 2 inclinometric accelerometers to record posture in-hospital and an ankle accelerometer to record ambulatory activity in-hospital and 30 days after discharge. Function was assessed on the day after discharge (Timed Up and Go [TUG], Short Physical Performance Battery [SPPB], hand grip strength) and 30 days after discharge. Length of stay was 5.1 ± 3.9 days. Participants spent 63.0 ± 19.2% of their hospital time lying down, 30.2 ± 18.7% sitting, 5.3 ± 4.2% standing, and 1.9 ± 8.6% ambulating. Thirty-day mean post-discharge stepping was 4890 ± 2285 steps/day. Each 10% increase in hospital lying time was associated with 0.7 s longer TUG time (95% confidence interval [CI] 0.2–1.9) at 30 days. Each 1000 additional daily steps in the post-discharge period was associated with a 0.8-point higher SPPB score (95% CI 0.1–1.0) at 30 days. Handgrip strength was unchanged.Older patients with heart failure were sedentary during hospitalization, which may contribute to decreased functional performance. Physical activity after discharge may minimize this negative effect.