Hospital-acquired functional decline can lead to poor health outcomes for frail older adults. This multicenter, prospective cohort study set in Japan assessed the effect of hospital-acquired function decline on post-discharge outcomes among older adults who had undergone cardiac surgery. The study observed poor prognostic outcomes in one-third of patients. Hospital-acquired functional decline was an independent predictor of poor prognosis. The authors encourage hospitals to develop and implement approaches to preventing functional decline in older adults.