Patients were recruited from consecutive admissions at a hyperacute stroke unit and were screened for risk of malnutrition (light, moderate, or severe) using CONUT scores. At the next visit, 3-month outcomes were obtained. Of the 164 recruited patients, 51.2% were male. Mean patient age was 77.7 (SD = 7.0) years, and 85.8% of patients had an ischemic stroke. There was a significant difference in the survival rate (p < .001) at 3 months between patients with moderate risk for malnourishment compared to the other patients. The multivariate regression Cox model showed that moderate risk of malnourishment, according to the CONUT score, increased the risk for death at 3 months (hazard ratio = 1.086; 95% CI [1.057, 8.305]; p < .039). The CONUT score has predictive validity for all-cause mortality in stroke patients after 3 months, both in hospital and after discharge. Further prospective multicenter studies with larger samples are needed to clarify the usefulness of the CONUT score in the prognosis of all-cause mortality in stroke patients.