Background Pre-existing dementia was related to poor functional outcome after intracerebral hemorrhage (ICH), and its commonly underlying pathologies were considered as cerebral amyloid angiopathy. But the impact of pre-existing dementia on in-hospital mortality in Chinese ICH patients has not been well characterized. Objective To investigate the association between pre-existing dementia and in-hospital mortality after ICH. Methods Data were extracted from the China Stroke Center Alliance database. Information about the existence of prior to stroke dementia was obtained from next of kin informants and registered in clinical charts. Patients’ characteristics, in-hospital mortality, home discharge and complications were compared between ICH patients with and without pre-existing dementia. Results Out of the 72,318 ICH patients, we identified 328 patients with pre-existing dementia. Patients with pre-existing dementia were more likely to experience greater stroke severity as measured by the National Institute of Health Stroke Scale and Glasgow Coma Scale. In the adjusted models, the presence of pre-existing dementia was associated with an increased risk of in-hospital mortality (OR 2.31, 95% CI 1.12–4.77), more frequent in-hospital complications of pulmonary embolism (OR 5.41, 95% CI 1.16–25.14), pneumonia (OR 1.58, 95% CI 1.08–2.33), urinary tract infection (OR 2.37, 95% CI 1.21–4.64), gastrointestinal bleeding (OR 2.39, 95% CI 1.27–4.49) and lower home discharge (OR 0.59, 95% CI 0.38∼0.93). Conclusions ICH patients with pre-existing dementia are more likely to suffer from greater stroke severity, poorer outcomes and lower home discharge. Future studies should evaluate the value of intensive risk factor control among individuals with pre-existing dementia for stroke prevention.