Objectives: Our primary aim was to determine the factors leading to prophylactic endotracheal intubation in intensive care unit (ICU) patients undergoing gastrointestinal endoscopy. Secondary aims were to determine the rate of unplanned endotracheal intubations during endoscopy and to determine the rate of aspiration following endoscopy for patients admitted to the ICU. Methods: Critically ill adult (≥18 years) patients who underwent upper and lower endoscopic procedures from January 2012 to July 2016 in a medical/surgical ICU were included. Determinants of prophylactic endotracheal intubation prior to endoscopy as well as other postprocedure outcomes were electronically captured by a validated data mart system. Given our focus on aspiration in those who were not endotracheally intubated prior to endoscopy, we used a validated definition a priori. Results: A total of 320 patients were included in the final analysis: 76(24%) were intubated prior to endoscopy and 244 (76%) were not. The endotracheally intubated group had a significantly higher Acute Physiologic and Chronic Health Evaluation III (44.5 [16.2] vs 39.5 [15.5]; P = .02) and Sequential Organ Failure Assessment (6.9 [4.4] vs 3.8 [3]; P ≤ .01) scores, higher rate of hematemesis within 24 hours of endoscopy (28 [37%] vs 45 [18%]; P ≤ .01), and higher rate of upper endoscopy (72 [96%] vs 181 [74%]; P ≤ .01). We composed a composite outcome for multivariable analyses, which demonstrated the rate of any complication was significantly higher among those who were intubated prior to the procedure versus those who were not intubated previously (odds ratio: 2.80, 95% confidence interval (CI): 1.16-6.72, P = .02). Conclusion: Endoscopy performed in the ICU without endotracheal intubation is safe. However, patient selection for prophylactic intubation prior to endoscopy is of critical importance as illustrated in this study with higher illness severity, planned upper endoscopy, and hematemesis 24 hours prior being key factors on deciding to perform endotracheal intubation. Prophylactic intubation for endoscopy and preexisting cardiac disease were associated with a higher rate of adverse outcomes.