An otherwise healthy 30-year-old male acquired gastrointestinal beriberi and subsequent Wernicke's encephalopathy after 1 session of heavy drinking. Nausea, vomiting, and anorexia relentlessly progressed. The patient developed external ophthalmoplegia after 2 months. Intravenous 1,000 mg thiamine reversed both neurologic and gastrointestinal symptoms within hours. It is hard to diagnose gastrointestinal beriberi since the symptoms are nonspecific. The patient underwent 11 emergency room visits, 3 hospital admissions, and laparoscopic cystectomy within 2 months, but the gastrointestinal symptoms continued to progress. Two months after the onset of gastrointestinal symptoms, external ophthalmoplegia appeared, and, therefore, intravenous thiamine was given. The simultaneous resolution of the debilitating gastrointestinal symptoms and external ophthalmoplegia was unique. Thiamine deficiency remains underdiagnosed and should be considered in patients who develop unexplained gastroparesis or autonomic nervous failure of the digestive system, even in the nonalcoholic population.