Hyponatremia can be asymptomatic or have a wide range of clinical presentations such as headaches, muscle cramps, nausea, seizures, coma, cerebral edema and may even result in death. Despite it has been suggested that duloxetine has a relatively less risk of hyponatraemia, the number of case reports are increasing. A 45-year old female patient with complaints of fear, anxiety, sleeplessness and headache was started on duloxetine (30 mg/day). In the first week of the treatment, she was admitted to the emergency service with dizziness, dry mouth, polyuria and polydipsia. She had to be transferred to the intensive care unit because of agitation, loss of consciousness and a generalized tonic-clonic seizure. Blood levels of Sodium (Na+), Potassium (K+) and Chlorine (Cl-) were, respectfully, 121 mmol/L, 2.7 mmol/L and 87 mmol/L. Brain imaging displayed cerebral edema. Electrolyte levels were regulated with saline infusions. Amitriptyline was initiated for the ongoing headache and anxiety. In outpatient visits, hyponatremia did not recur in the following 3 months.