Background: Influenza can cause severe acute respiratory illness (SARI), which occurs as local outbreaks or seasonal epidemics with high intensive care unit (ICU) admission and mortality rates. Mortality is mainly due to SARI. Objective: The aim of this study was to evaluate the outcome of patients admitted to ICU due to influenza-related SARI in 2017-2018 flu season in Turkey. Methods: A retrospective multicenter study was conducted in 13 ICUs with a total of 216 beds from 6 cities in Turkey. All adult patients (over 18 years) admitted to the ICUs in 2017-2018 flu season (between September 1, 2017, and April 30, 2018) because of SARI and with a positive nasopharyngeal swab for influenza were included in the study. Results: A total of 123 cases were included in the study. The mean age of patients was 64.5 +/- 17.5 years, and 66 (53.7%) patients were older than 65 years. The ICU mortality was 33.9%, and hospital mortality was 35.6%. Invasive mechanical ventilation (IMV), acute kidney injury (AKI), hematologic malignancy, and >65 years of age were the factors affecting mortality in influenza. Conclusion: SARI due to influenza carries a high mortality rate, and IMV, AKI, presence of hematologic malignancy, and older age are independent risk factors for mortality.