Objective: To determine the type of electrolytes abnormalities observed among critically ill patients of NICU and PICU. Material and Methods: A Hospital based prospective and observational study conducted among 99 critically ill patients between 0 to 15 years age. Results: Out of total patients,78 (78.8%) cases had abnormal electrolytes level, and 21(21.2%) cases had normal electrolytes level. 10(12.8%) cases had imbalance of single electrolyte, 17(21.7%) cases had imbalance of two electrolytes, 16(20.5%) cases had imbalance of three electrolytes, and 35(44.8%) cases had imbalance of more than three electrolytes. This shows that majority of patients in PICU had multiple electrolyte (>3) abnormalities. In our study, maximum prevalence is of sodium abnormalities 63(63.6%) followed by potassium abnormalities 50(50.5%). Calcium, Phosphate and Chloride has same prevalence 40(40.3%). Conclusion: Our study findings conclude that maximum prevalence 80.7% is of sodium abnormalities. Hyponatremia is most common electrolyte abnormalities present in 63.5% cases. Early recognition with a thorough understanding of common electrolyte abnormalities and their prompt management definitely pose an implication on the final outcome of the patient. Aggressive & strict adherence to correction of in particular to sodium and potassium before weaning is necessary for successful weaning from ventilator.