Background: Serum procalcitonin (PCT) is already known predictive marker in serious bacterial infection and it is emphasized that these biomarkers can be used as a marker of increased mortality in critically ill patients. The aim of the study was to evaluate the serial PCT level and find out whether these biomarkers can be used to predict mortality.   Methods: This was a prospective observational study. Primary objective was to study the serum PCT as a prognostic marker in critically ill children (2 months to 12 years) admitted in PICU while secondary objective was to find out the association of level of serum procalcitonin with different organ system disease involvement and to compare the results of the serum procalcitonin with the PRISM-3 score in diagnosing the severity of illness in the patient. Patient outcome was assessed at hospital discharge, and the patients were divided into non-survivors and survivors. A p value of <0.05 will be considered statistically significant. Results: A total of 185 patients were enrolled, the median age was 5 years (2 months to 12 years) with 56.76% being males. Majority (34.59%) of patients the primary diagnosis was of respiratory system. The median of serum PCT on day 1, day 3 and day 7 with outcome (p<0.05) in dead was significantly higher as compared to alive. The median PRISM score in dead was 21(13-33) which was significantly higher as compared to alive 11 (8-12.7). Serum PCT and PRISM score had significant discriminatory power to predict mortality.   Conclusions: In the present study serum PCT found to be a good prognostic marker for all cause mortality in critically ill patients admitted in PICU.