Background: Hyponatremia is a common electrolyte imbalance which occurs in children with pneumonia. Many studies have reported the incidence of hyponatremia around 40 to 45%.Presence of hyponatremia adds to the morbidity apart from the disease itself. Hence the present study wastaken up to find the incidence of hyponatremia in pneumonia. Methods: This prospective observational study involved 122 children admitted to the paediatric ward and PICU of PMCH, Patna. Children diagnosed as pneumoniaas per WHO guidelines between 1 to 5 years were included. Beside other relevant blood investigations, blood samples for electrolytes were analysed using automated analyser that uses ISE (ion selective electrode) technology for sodium determination. Conclusion: Hyponatremia is common electrolyte imbalance found in community acquired pneumoniaand more commonly seen in severe pneumonia.