Abstract Background Craniopharyngiomas are low‐grade malignancies (WHO I) in the sellar region. Most cases of childhood‐onset craniopharyngioma are adamantinomatous craniopharyngioma, and neurosurgery is the treatment of choice. Affected patients have postoperative complications, including water and electrolyte disturbances, because these malignancies develop near the hypothalamus and pituitary gland. Determining postoperative serum sodium fluctuation patterns in these patients can reduce postoperative mortality and improve prognosis. Objective To measure changes in serum sodium levels in pediatric patients who underwent craniopharyngioma surgery and identify influencing factors. Methods This retrospective study measured the serum sodium levels of 202 patients aged 0–18 years who underwent craniopharyngioma resection in Beijing Tiantan Hospital and Beijing Children's Hospital and identified predictors of severe hyponatremia and hypernatremia. Results The mean age of the cohort was 8.35 ± 4.35 years. The prevalence of hypernatremia, hyponatremia, and their severe forms (serum Na+ > 150 mmol/L and serum Na+