Cyclospora cayetanensis is a coccidian protozoa that was newly recognized in 1979 in Papua New Guinea. We report the case of a 42-year-old French man who had visited Vietnam and presented with fever and watery diarrhea that had lasted for more than 2 weeks. The patient was diagnosed with C. cayetanensis infection by examination of a stool smear using UV fluorescence microscopy. Based on this rare case, we recommend that Cyclospora infection might be considered in the differential diagnosis of traveler's diarrhea in immunocompetent patients.