Objective A dengue outbreak occurred in Japan 2014. We investigated the characteristics of dengue infection among Japanese. Methods We investigated the medical charts retrospectively. Patients The study participants are patients who came to our clinic between 2008 and 2014. Results We investigated 4 domestic cases and 46 imported cases of Japanese with laboratory confirmation of dengue. Major symptoms were fever (100%), rash (86%), fatigue (84%), headache (81%), joint pain (66%), muscle pain (49%), and bleeding (6%). A late rash that appeared near the time of fever resolution was observed in 37 cases (74%). A total of 38/43 (88%) cases had low WBC count (<3,500/μL) during the febrile period, 42/48 (88%) cases had a low platelet (PLT) count (<130×10 3 /μL), and 44/50 (88%) cases had a C-reactive protein (CRP) <2.0 mg/dL. Conclusion Patients with a high fever, late rash, fever-associated leukopenia, low PLT count, low CRP, and elevated aminotransferases are generally suspected of having a dengue infection.