The association of apathy with Alzheimer disease and other dementias and caregiver burden has been examined in a number of studies; however, less is known about its relationship with delirium and mortality. We aimed to investigate the prevalence, relationship with delirium and dementia, and prognostic value of apathy in an elderly and frail inpatient population. The cohort included 425 patients in acute geriatric wards and in 7 nursing homes in Helsinki (1999-2000). Demographic factors, physical functioning, diagnoses, and drugs were assessed with special reference for dementia, delirium, and apathy. Mortality was registered from central registers. Of the patients, 98 (23.1%) suffered from apathy, and it was more frequent among men (32% versus 21% women, P = .037 ). There was no difference in mean age, number of comorbidities, or in the mean number of medications between those with and without apathy; however, those with apathy had lower mean MMSE points (9.2 versus 14.0 without apathy, P < .001), more often severe dementia according to Clinical Dementia Rating, and higher dependence in activities of daily living (P = .001). Furthermore, patients with apathy were more often suffering from delirium (37.8% versus 21.1%, P ≤ .001). Mortality during the 1-year follow-up was 34.7% (n = 34) and 22.0% (n = 72) among individuals with and without apathy, respectively (P = .011). In the Cox proportional hazard model with age, gender, activities of daily living, and delirium as covariates, apathy significantly predicted mortality (HR 1.89, 95% CI 1.24 to 2.89; P = .003). Apathy is a common and serious neuropsychiatric symptom associated with cognitive decline, delirium, and disability, and it also independently predicts mortality.