Introduction: Lower respirational tract infections (LRTIs) are common during childhood and can have high morbidity and mortality rates if not treated. It is among the serious health problems specifically in less than 5 years of age requiring hospitalization and attributes to 30% of deaths yearly worldwide especially due to pneumonia as the leading cause. Aim of the study: Aim of the study was to identify the hyponatremia in children with pneumonia. Material & Methods: This prospective study was conducted in Plasma maternity & general hospital, Bangabandhu Avenue, Oxygen moor Chittagong. The study period was from January, 2019 to December, 2019. A total of 120 patients were included for the study. Other investigations were done whenever required. Collected data were analyzed by frequencies, percentages, mean, and standard deviation and by Chi-square test by using SPSS 16.0. Results: The mean age of children was 1.3 (±) 2.5 years. Maximum number of children (60%) belonged to age group between 2 months to 12 months while the least number of children (18%) belonged to age group between 3 to 5 years. Male to female ratio was 2.1:1. In children with moderate hyponatremia 16% of them suffered from moderate pneumonia and 10% had very severe pneumonia and 4% had pneumonia. Among children with pneumonia 12% had pneumonia only while 2% had severe pneumonia and 6% had very severe pneumonia. Conclusion: Hyponatremia is prevalent in children with pneumonia. The children admitted with pneumonia have higher morbidity when associated with hyponatremia. In our study too hyponatremia was detected in children with pneumonia that was statistically significant.