Background: Electrolyte disturbance is one of the complications of subarachnoid hemorrhage (SAH) and its prognostic value is not fully understood. The focus of this study is to evaluate the impact of dysnatremia and dyskalemia on functional outcomes in patients with aneurysmal SAH. Materials and methods: Patients with spontaneous aneurysmal SAH who were admitted to our intensive care unit (ICU) between 1st January 2011 and 31st December 2016 were included. Demographic data, biochemical parameters from days 1 to day 11 of ICU admission, disease severity, and clinical outcome were recorded. The prognosis was estimated using the Glasgow outcome scale (GOS) at 3 months after the initial insult. Results: A total of 244 patients were included in this study. There were 139 patients (57.0%) with hyponatremia (Na < 135 mmol/L) while 82 patients (33.6%) had hypernatremia (Na >146 mmol/L). Hyponatremia, hypernatremia, and sodium fluctuation >12 mmol/L were more commonly found in those patients with poor outcome. However, both hypokalemia and hyperkalemia were not shown to have a significant effect on the patient's prognosis. Logistic regression analysis identified the following independent predictors of poor outcome (GOS 1-3 at 3 months): age >55 years old, acute physiology and chronic health evaluation IV (APACHE IV) score >50, World Federation of Neurosurgical Societies (WFNS) grade >3, Fisher grade >2, presence of intracranial hemorrhage (ICH)/intraventricular hemorrhage (IVH), use of mannitol, use of loop diuretic aneurysms, involving posterior circulation, and hypernatremia >146 mmol/L. Conclusion: Hypernatremia, but not hyponatremia, in patients with aneurysmal SAH is associated with poor outcome. Both hypokalemia and hyperkalemia were not shown to have a significant effect on the patient's prognosis. Further studies are required to determine whether the treatment of dysnatremia can influence outcomes. Clinical significance: Dysnatremia and dyskalemia are common in patients with aneurysmal SAH, but only hypernatremia is associated with poor outcome. Further studies are required to determine whether the treatment of dysnatremia can influence outcomes.