Purpose: Unclear recommendations in transfusion guidelines may possibly lead to inconsistency in treatment of patients admitted to the intensive care unit. This study aimed to uncover variation in red blood cell (RBC) transfusion decisions in the ICU worldwide. Methods: Members of the European Society of Intensive Care Medicine (ESICM) were requested to complete an online questionnaire which included four different hypothetical clinical scenarios. The scenarios represented patients with acute myocardial infarction (AMI), abdominal sepsis, traumatic brain injury (TBI) and post-surgical complications. Hemoglobin level was 7∙3 g/dL in all scenarios. The questionnaire explored the physicians' transfusion decision in each clinical scenario and identified patient characteristics that were most influential in the transfusion decision. Results: In total 211 members participated in the study, of whom 142 (67%) completed the entire survey. Most variation was observed in the clinical scenario of sepsis, in which 49% decided to transfuse and 51% decided not to. In the clinical scenarios of AMI, TBI and post-surgical complications this was respectively; 75/25%, 35/65% and 66/34%. Conclusions: Critical care physicians differed in outcome of RBC transfusion decisions and weighed patient characteristics differently. These findings indicate that variation in transfusion practice amongst critical care physicians exists.