In Kawasaki disease (KD), convulsions are rare and mostly attributed to latent and coexisting encephalitis/encephalopathy due to KD itself. Therefore, we retrospectively investigated concomitant viral infections in patients with KD. Between January 2012 and December 2020, among 523 patients with KD, 7 (1.53%), 1 (0.19%), 6 and 1 (1.15% and 0.19%) were positive for adenovirus (AdV-Ag), respiratory syncytial virus (RSV-Ag), and influenza A or B (Flu A-Ag or Flu B-Ag) antigens, respectively. Among them, two were positive for both AdV-Ag and FluA-Ag. Seven patients with KD (1.3%) presented febrile convulsions, and only one was diagnosed with encephalitis/encephalopathy. Between January 2021 and August 2022, 57 patients with KD were newly diagnosed among whom FilmArray® respiratory panel (FARP) was applied on 24 patients, and 14 (58.3%) were positive for at least one virus. During the same period, 32 out of 45 patients (71.1%) with febrile convulsions examined using the FARP were positive for at least one virus. The trend of viruses in patients with KD and febrile convulsion reflected the regional epidemic viral infection. Respiratory virus detected at a much higher rate using the FARP suggests that most convulsions in patients with KD might be related to concomitant viral infection. The possible involvement and association of concomitant respiratory viral infections in patients with KD with prognosis or encephalopathy/encephalitis remain to be investigated.