We assessed the clinical impact of thrombelastography (TEG®) results (TEG® 5000, Haemonetics Corporation, Braintree, MA, USA) by measuring their ability to cause changes in a theoretical treatment plan and contribute to the understanding of haemostasis. We prospectively included paediatric intensive care unit (PICU) patients who had standard tests of haemostasis and TEG ordered and had an arterial catheter or extracorporeal access port in situ. Blood for standard tests and TEG was taken simultaneously. Independent of patient care, general patient information and results of standard laboratory tests were presented to five clinicians who were asked to document their theoretical treatment plan. Clinicians were then shown TEG results and asked if they caused a change in their plan, if they confirmed initial standard laboratory test results, if they enabled a better understanding of haemostasis and if they provided additional information. Inter-rater agreement between the clinicians was determined. Forty-two TEG results were obtained from 34 patients. Overall, the inclusion of TEG results led to a change in treatment plan in 97 of 207 occasions (47%), confirmed standard laboratory test results in 177 of 204 occasions (87%), enabled a better understanding of haemostasis in 140 of 204 occasions (69%) and provided additional information in 131 of 204 occasions (64%). Variation existed between clinicians, seemingly due to individual differences, with poor inter-rater agreement. We conclude that TEG results led to changes in treatment plans almost half the time, confirmed findings of standard tests and provided a better understanding of haemostasis, but randomised controlled trials are required to determine the role and influence of TEG results on patient outcome.