Objectives: This study aimed to evaluate the predictive validity of the day-1 PELOD-2 and day-1 "quick" PELOD-2 (qPELOD-2) scores for in-hospital mortality in children with sepsis in a pediatric intensive care unit (PICU) of a developing country. Methods: The data of 516 children diagnosed as sepsis were retrospectively analyzed. The children were divided into survival group and non-survival group, according to the clinical outcome 28 days after admission. Day-1 PELOD-2, day-1 qPELOD-2, pediatric SOFA (pSOFA), and P-MODS were collected and scored. Receiver operating characteristic (ROC) curves were plotted, and the efficiency of the day-1 PELOD-2, day-1 qPELOD-2 score, pSOFA, and P-MODS for predicting death were evaluated by the area under the ROC curve (AUC). Results: The day-1 PELOD-2 score, day-1 qPELOD-2 score, pSOFA, and P-MODS in the non-survivor group were significantly higher than those in the survivor group. ROC curve analysis showed that the AUCs of the day-1 PELOD-2 score, day-1 qPELOD-2 score, pSOFA, and P-MODS for predicting the prognosis of children with sepsis in the PICU were 0.916, 0.802, 0.937, and 0.761, respectively (all p < 0.05). Conclusions: Both the day-1 PELOD-2 score and day-1 qPELOD-2 score were effective and able to assess the prognosis of children with sepsis in a PICU of a developing country. Additionally, the day-1 PELOD-2 score was superior to the day-1 qPELOD-2 score. Further studies are needed to verify the usefulness of the day-1 qPELOD-2 score, particularly outside of the PICU.