A 68-year-old Japanese man presented with Ascaris lumbricoides discharge from his mouth. The infection was suspected to have occurred while the patient was in the Philippines. This A. lumbricoides migration occurred because a proton pump inhibitor was used and Billroth I resection had been performed, which reduced gastric acid secretion and increased gastric pH. In addition, the pylorus had been removed during Billroth I resection, enabling easy access to the stomach. The number of imported foods, of infected migrants and refugees, and of overseas travels is increasing, and these factors may lead to an increase in A. lumbricoides infection even in countries with a typically low incidence of such infections. Clinicians should bear in mind that parasitic infections may occur in nonendemic areas.