This is a case of a 40-year-old Japanese adult male who had acute onset watery diarrhoea with intermittent abdominal discomfort. Several days later, he found a 1 metre of tape-shaped object emerged from his anus and was eventually admitted to our hospital for further investigation. Stool examination revealed eggs of Diphyllobothrium with characteristic shape in his stool. After oral praziquantel administration, segments of proglottids were expelled from his anus. The proglottids were sent to the Infectious Disease Surveillance Centre of Japan, and DNA analysis of the proglottids proved to be those of Diphyllobothrium nihonkaiense. The patient confessed that he had an eating habit of chilled salmon. His diarrhoea and abdominal discomfort were completely diminished after 1 day of oral praziquantel administration. He was successfully discharged from the hospital a few days later admission without any complication of the disease and the side effect of treatment.