In children, acute liver failure (ALF) is a severe condition associated with high mortality if an emergency liver transplantation (LT) is impossible. Clinical laboratory parameters and different scores or criteria are used to predict ALF evolution in children. We aimed to assess the role of coagulation factors as predictive markers of poor outcomes in children with ALF. The prospective study included 40 children with ALF, diagnosed based on the Pediatric ALF study group criteria. Patients with emergency LT or deceased were considered with poor outcomes. For all patients, we analyzed clinical and laboratory parameters (including plasma level of factor V (FV), factor VII (FVII), and INR). We calculated the PELD (Pediatric End-stage Liver Disease) and MELD (Model for End-stage Liver Disease) scores, King's College Hospital (KCH), and Clichy criteria. We analyzed their performance in predicting a poor outcome. FV and FVII levels were significantly lower in children with poor outcomes than survivors (18.92 ± 19.95% vs. 10.72 ± 10.21%, p = 0.00139, respectively 46.51 ± 26.05% vs. 10.72 ± 10.21%, p = 0.00014). These parameters varied with ALF etiology, being the lowest in metabolic and infectious causes. The maximum value of INR (INR-max) was higher in children with poor outcomes than survivors (7.05 ± 3.20 vs. 2.96 ± 1.82, p = 0.000007), as it also was for the PELD/MELD score (30.06 ± 15.55 vs. 15.77 ± 9.64, p = 0.00092). FVII, FV, and INR-max had an excellent performance in predicting the poor outcome with an area under the ROC curve of 0.894, 0.816, and 0.861, respectively. KCH criteria had a higher sensitivity than Clichy criteria (92.86% vs. 50%) but lower specificity (53.85% vs. 95%). Our results support the role of coagulation factors (INR, FV, and FVII) as predictive markers for the fatal evolution of children with ALF and underlined the need for monitoring along with the usual liver function tests in children with ALF.