Transfusion is a common practice during neurosurgery. However, there is no evidence-based consensus on transfusion practice in neurosurgery. This review summarizes the evidence pertinent to the commonly used transfusion triggers in neurosurgical patients. In the field of neurosurgery, there is only one randomized controlled trial, performed in patients with traumatic brain injury, to investigate the transfusion trigger of red blood cells. There is a lack-of-quality evidence pertinent to the transfusion triggers of other blood products. Most of the transfusion triggers used for neurosurgical patients are extrapolated from the evidence based on studies performed in nonneurosurgical patients. Clinical experience and expert opinions have played a major role in transfusion practice in neurosurgery. There is a scarcity of high-quality outcome-based evidence for transfusion practice in neurosurgery. In the absence of quality evidence, the transfusion practice in neurosurgical patients should be based on the understanding of the complex pathophysiology related to anemia and coagulopathy and the balance between the risks and benefits associated with blood product transfusion. The practice guided by tissue oximeter and viscoelastic tests appears promising, but needs to be validated by future studies.