Because of the potential adverse events and teratogenesis of antipsychotic drugs, it is important to find a safe and effective treatment for pregnant women with severe mental illness. The membrane hypothesis of schizophrenia provides a rationale to treat symptoms of schizophrenia with omega-3 PUFAs. We report a 30-year-old married woman with chronic schizophrenia, who experienced an episode of acute exacerbation of psychotic symptoms during pregnancy. After entering into an open trial of omega-3 PUFAs monotherapy, she showed a dramatic improvement in both positive and negative symptoms of schizophrenia and a significant increase of omega-3 PUFA composition in erythrocyte membrane. There were no adverse effects in this treatment. Thus, omega-3 PUFAs could be both beneficial and therapeutic to pregnant schizophrenic women.