Background: Any type of surgical trauma whether elective or emergency causes various effects on the human body including a great impact on the physiology of fluid and electrolytes within the body. Mortality and morbidity is very common due to the fluid imbalance after major surgical trauma. Aim: the aim of this study was to assessment of alterations in serum potassium levels during postoperative exploratory laparotomy. Materials and methods: This is a retrospective study conducted in the Department of Paediatrics surgery Patna Medical College and Hospital, Patna, Bihar, India and Sushrut Child Surgery Centre, Patna, Bihar from January 2016 to January 2020.. A total of 50 patients who underwent explorative laparotomy were include in this study. Collection of 2 cc of blood volume was done at preoperative time, one the day of surgery and on postoperative days of surgery. All the samples were sent to laboratory where autoanalyzer was used for assessment of serum potassium levels. Results: Mean age of the patients was 16.7 years. 70 percent of the patients were males while the remaining were females. Mean potassium levels at Baseline (before starting of surgery), One day after surgery, Three days after surgery and Seven days after surgery were found to be 4.85 mEq/L, 5.24 mEq/L, 4.41 mEq/L and 4.32 mEq/L respectively. A significant reduction in the potassium levels during the initial postoperative phase was seen followed by a significant rise; thereby returning to normal value 1 week postoperatively. Conclusion: we concluded that the significant rise in the potassium levels occur after exploratory laparotomy, followed by restoration to normal values by the end of first postoperative week.