Ovarian hyperstimulation syndrome (OHSS) is one of the most important complications of assisted reproductive technologies. Mild OHSS is characterized by ovarian enlargement and abdominal discomfort. In severe cases anasarca, hepatic dysfunction, reduced blood volume, electrolyte imbalance, organ failure and thromboembolic phenomena may be observed. Delirium is a syndrome, not a disease, and has many causes, all of which result in a similar pattern of signs and symptoms relating to a patient's level of consciousness and cognitive impairment. Delirium remains an under-recognized and under-diagnosed clinical disorder. The case is presented of a 30-year-old woman with OHSS and delirium. She underwent intracytoplasmic sperm injection (ICSI) for severe male factor infertility. Five days after oocyte retrieval, ascite formation was observed in ultrasonographic evaluation, and embryo transfer was cancelled. Twelve days after retrieval she came to the emergency clinic with abdominal distension and pain. She was hospitalized and paracentesis was performed every other day three times. She had altered consciousness and psychomotor hypoactivity 1 h after the last paracentesis. Psychiatric consultation revealed that she was in a state of delirium, and haloperidol was administered for treatment. Her symptoms disappeared within a week. Her medication was stopped when symptoms resolved and she was still asymptomatic in psychiatric evaluation 1 week later.