PURPOSE: Infectious encephalitis (IE) is a severe disease which requires intensive care unit (ICU) admission in up to 50% of cases. We aimed to describe characteristics, management and outcomes of IE patients who required ICU admission. MATERIALS AND METHODS: Ancillary study focusing on patients with ICU admission within the ENCEIF cohort, a French prospective observational multicentre study. The primary criteria for outcome was the functional status at hospital discharge, categorized using the Glasgow outcome scale (GOS). Logistic regression model was used to identify risk factors for poor outcome, defined as a GOS ≤ 3. RESULTS: We enrolled 198 ICU patients with IE. HSV was the primary cause (n = 72, 36% of all IE, 53% of IE with microbiological documentation). Fifty-two patients (26%) had poor outcome at hospital discharge, including 22 deaths (11%). Immunodeficiency, supratentorial focal signs on admission, lower cerebrospinal fluid (CSF) white cells count (2 days were independent predictors of poor outcome. CONCLUSION: HSV is the primary cause of IE requiring ICU admission. IE patients admitted in ICU have a poor prognosis with 11% of in-hospital mortality and 15% of severe disabilities in survivors at discharge.