Hematological consequences of novel antiseizure medications (ASMs) or combined therapies are rarely reported, especially in pediatric patients undergoing surgery for epilepsy. This study aimed to assess the prevalence and risk factors of coagulation dysfunction in this population and evaluate their relationship with intra- and postoperative bleeding. Three hundred ninety children who underwent surgery for epilepsy and 104 children without epilepsy who underwent nonepilepsy surgery at the authors' center were included in the study. The authors retrospectively collected and analyzed the following clinical data: sex, age, weight, course of epilepsy, antiseizure therapy, first laboratory data after admission, and transfusion-related data. ASMs were responsible for the higher incidence of coagulation dysfunction in pediatric epilepsy surgery patients. Low body weight (OR 0.95, 95% CI 0.92-0.98) and valproic acid (VPA) therapy (OR 5.13, 95% CI 3.25-8.22) were the most relevant factors leading to coagulation dysfunction. The most common hematological side effects of VPA were thrombocytopenia and hypofibrinogenemia, whereas low body weight was only associated with hypofibrinogenemia. Both VPA and low body weight increased the need for intra- or postoperative transfusion (p < 0.001). Pediatric epilepsy surgery patients often take multiple ASMs, resulting in an increased incidence of coagulopathy. VPA levels and low body weight were found to be the main influential factors associated with an increased risk of coagulation dysfunction. Platelet and fibrinogen levels were the main indices that were affected. Both VPA and low body weight were relevant to additional surgery-related transfusion, necessitating the need for increased awareness of preoperative coagulopathy before pediatric epilepsy surgery. Clinical trial registration no.: NCT05675254 (ClinicalTrials.gov).