Background To estimate the incidence, risk factors, and impact on mortality and functional outcomes for early coagulopathy after the return of spontaneous circulation (ROSC) in pediatric out-of-hospital cardiac arrest (OHCA) patients. Methods A post hoc analysis of the Therapeutic Hypothermia after Pediatric Cardiac Arrest Out-of-Hospital (THAPCA-OH) trial was conducted. Early coagulopathy was defined as presence of at least one of the following coagulation abnormalities upon admission: international standard ratio (INR), platelets, and age-adjusted activated partial thromboplastin time (APTT) within 6 h after OHCA and before therapeutic hypothermia initiation. The outcomes included 28-day mortality and functional prognosis. Multivariable logistic regression models were used to explore risk factors and association between early coagulopathy and outcomes. Results Of the 227 patients included, 152 (67%) were male and the median age was 2.3 years [interquartile range (IQR), 0.7-8.6 years]. The overall 28-day mortality was 63%. The incidence of early coagulopathy was 46%. Lower age, longer duration of chest compression, lower temperature, and higher white blood cell (WBC) upon admission increased the risk of early coagulopathy. Early coagulopathy [OR, 2.20 (95% CI, 1.12-4.39), P = 0.023] was independently associated with 28-day mortality after adjusting for confounders. Conclusions Early coagulopathy occurred in almost half of pediatric patients with OHCA. Lower age, longer duration of chest compression, lower temperature, and higher WBC increased the risk. The development of early coagulopathy was independently associated with increased mortality.