Hookworm is one of the most common parasites in the world, but can be missed on stool examination. We report a 31-year-old man who was complaining of epigastric discomfort, with laboratory findings of iron-deficiency anemia and eosinophilia. He was found to be infected with hookworm (Ancylostoma duodenale), which was directly detected and retrieved from the duodenum with biopsy forceps during upper gastrointestinal endoscopy. We eliminated his infection successfully by the Damaso de Rivas-Kihara modified method and oral administration of pyrantel pamoate. This report indicates that it is important to check carefully even in the distal duodenum at routine upper gastrointestinal endoscopy whenever parasitic disease is suspected but is hard to diagnose because of a limited number of eggs in feces.