Purpose <p>Sodium imbalance are common complications after transsphenoidal surgery (TSS) for pituitary neuroendocrine tumors (PitNETs). We characterized the types of sodium imbalance, identified risk factors for these disorders, and provided corresponding treatment advice.</p> Methods <p>We screened patients who had undergone TSS for PitNETs at a single center to identify those who did and did not (control) develop sodium imbalance. Disorders were classified using three groups, based mainly on the serum sodium level and degree of daily increase or decrease therein. We performed multivariable logistic regression analysis to identify risk factors among numerous variables (patient characteristics, third ventricle deformation, tumor volume, maximum tumor diameter, hydrocephalus, cerebrospinal fluid rhinorrhea, and pituitary target gland axes).</p> Results <p>The sample comprised 105 patients with and 129 patients without sodium imbalance. Logistic regression analysis showed that hydrocephalus [<i>P</i> = 0.0015, odds ratio (OR) = 7.112, 95% confidence interval (CI) 1.475–34.3], cerebrospinal fluid rhinorrhea (<i>P</i> &lt; 0.001, OR = 4.62, 95% CI 2.372–9), and preoperative hypothalamus–pituitary–gonadal (HPG) axis hypofunction (<i>P</i> = 0.009, OR = 3.211, 95% CI 1.341–7.691) were independent risk factors sodium imbalance development after TSS. Compared with the control, risk factors differed among disorder groups.</p> Conclusion <p>This study showed that cerebrospinal fluid rhinorrhea, hydrocephalus, and preoperative HPG axis hypofunction are risk factors for sodium imbalance development after TSS for PitNETs. We divided sodium imbalances into three groups to guide treatment.</p>