Objectives. To describe a case of fluvoxamine-induced severe hyponatremia, most likely due to abnormal antidiuretic hormone excretion (SIADH), and to discuss the implication for maintenance treatments for these patients. Clinical Observations. Although this syndrome had its incidence most commonly among the elderly, we report a case of severe hyponatremia (serum sodium <114 mmol/L), in a relatively young male. Treatment. Symptoms responded well to IV hyperosmolar sodium and to the discontinuation of fluvoxamine. This patient was maintained for treatment on an alternative Selective Serotonin Reuptake Inhibitor (SSRI), Citalopram, without developing recurrence of symptoms. Outcome and Conclusion. Protocols to monitor the maintenance treatments in high-risk patients may be needed to prevent recurrence of serious complications.