The staff of an Australian hospital faced significant challenges in evacuating the whole hospital due to unprecedented flooding. A retrospective study of those challenges and consequent adaptations was conducted to capture lessons for better preparedness. Semi-structured interviews with seven clinicians and nurse managers in critical roles during the evacuation were conducted. Inductive thematic analysis was conducted in NVivo 14 to capture the themes emerging from the interview transcripts. Communication disruption, lack of knowledge of evacuation plan, staff shortage due to floods, crowd control of numerous volunteers, difficulties with ambulance service and insufficient information on field hospital's site and requirements, were the major challenges that the flood-affected hospital's staff faced during evacuation. The staff improvised by conducting a reverse triage of patients that were tracked throughout evacuation. Additional adaptations included usage of private cars, buses and maxi taxis to transport equipment, medication and supplies. Despite being rare, whole hospital evacuations cannot be ruled out at a time when climate change is increasing the frequency and intensity of disasters. This research identifies lessons to enhance disaster preparedness for potential hospital evacuations.