Although moderate therapeutic hypothermia is the only proven neuroprotective therapy in neonatal hypoxic ischemic encephalopathy secondary to perinatal asphyxia (PA), there is lack of data for its effect on hemostasis. To investigate the effect of neonatal asphyxia on hemostasis and to evaluate the effect of whole body cooling on hematological parameters. Hematological parameters evaluated on the first day of patients with PA before start of hypothermia were compared with those of healthy controls. The effects of whole body cooling on the same parameters were also evaluated on the fourth day. A total of 17 neonates with PA and 15 healthy controls were included. Mean values for prothrombin time (PT), international normalized ratio (INR), activated partial thromboplastin time (aPTT), and d-dimer obtained on the first day were significantly higher in the PA group compared to healthy controls (P <= .001 for all comparisons), whereas platelet count, levels of fibrinogen, factors II, V, VII, IX, X, and XI were significantly lower (P <= .005 for all comparisons). Levels of factor XIII were normal in both groups. In the study group, mean values for PT, INR, aPTT, and d-dimer evaluated on postnatal day 4 were significantly lower compared to values obtained on the first day of birth in PA group (P < .05 for all comparisons), with statistically significant increases in mean levels of fibrinogen, factor II, V, VII, IX, X, and XII (P < .05 for all comparisons). PA results in significant reductions in levels of factors of the extrinsic pathway and has been associated with thrombocytopenia and disseminated intravascular coagulation. Hypothermia may actually improve the clinical picture in such patients rather than aggravating the hemostatic disturbance, particularly with the implementation of supportive treatment.