Since its introduction in daily medical practice in the late 20th century, flexible bronchoscopy has had an increasing role in the everyday life of the pulmonologist. Not only for diagnosis, but also for therapeutic interventions, it has achieved widespread use and is now performed in a diversity of clinical scenarios. For several reasons, from easy performance in trained hands to versatility, diagnostic reliability, and safety, flexible bronchoscopy is now widely accepted and increasingly used in the management of critically ill patients. The knowledge of the unique features of intensive care unit patients, as well as indications and contraindications for the procedure, is paramount in achieving optimal results, while minimizing potential risks and complications. Performing bronchoscopy in an unstable patient, often on mechanical ventilation, requires awareness of the specific pathophysiological impact of the procedure. This in turn determines respiratory and cardiovascular derangements frequently observed during the procedure. This article reviews indications, pathophysiology, technical aspects, complications, and contraindications of flexible bronchoscopy in the critical care patient.