Neurological complications related to spinal anesthesia are exceptional, but their consequences are serious. We report a case of conversion disorder, which was initially diagnosed as monoplegia caused by spinal anesthesia. The patient was a 36-year-old, 88 kg woman with a history of psychogenic aphonia. She underwent plastic surgery for both toes under spinal anesthesia. On the following day, her left leg remained paralyzed with loss of sensation below the knee level. She practiced walking according to rehabilitation program, but paralysis became worse gradually. As the hospitalization was prolonged, she refused to be discharged from the hospital and began to demand the compensation. Her symptoms had not been correlated with the correct anatomical patterns of neurological deficit. The reflexes and muscle's tonus were normal and EMG gave normal findings. The result of neurological diagnosis, confirmed the diagnosis of conversion disorder causing her monoplegia because she was under psychic stressful circumstances from her family. Conversion disorder as a cause of monoplegia after surgery under spinal anesthesia should be kept in mind.