Background: The aim of this register-based cohort study was to characterize patients admitted to the intensive care unit (ICU) following non-cardiac surgery and identify risk factors associated with 30-days, 90-days and 1-year mortality after ICU admission. Methods: Patients aged 18+ years admitted to the intensive care unit within 30-days of non-cardiac surgery at four Capital Region hospitals in Denmark between January 2005 and December 2014 were included. Patients were identified through the Danish National Patient Register. The outcomes were 30-days, 90-days and 1-year mortality after ICU admission. Unadjusted and multivariate logistic regression analyses were performed to identify independent risk factors of mortality. Results: The study included 3311 ICU patients. Gastrointestinal surgery accounted for 71.3%, orthopaedic surgery for 18.4% and urologic surgery for 10.2% of the population. For the total population, the median length of stay in hospital was 18 days (9-36, 25th-75th percentile) and 2 days (1-4, 25th-75th percentile) in the ICU. Thirty-days, 90-days and 1-year mortality were 37.8%, 44.5% and 51.2% respectively. Mortality within the ICU was 22.3% while the post-ICU in-hospital mortality was 19.4%. Higher age, comorbidity, delayed ICU admission, acute surgery, and gastrointestinal and orthopaedic surgery increased 30-days, 90-days and 1-year mortality. Conclusions: Short- and long-term mortality in non-cardiac surgical patients admitted to the ICU is very high, especially among the elderly comorbid patients undergoing acute surgery. Future research should focus on targeting clinically modifiable risk factors and performing tailored treatment for these high-risk patients.