Japanese spotted fever is a tick-borne infectious disease caused by Rickettsia japonica. Early treatment is crucial to prevent deterioration and death. We present a case of an 82-year-old male with Japanese spotted fever coinciding with coronavirus disease 2019 (COVID-19). Initially diagnosed with COVID-19 via a severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) antigen test at a clinic and advised to recuperate at home, the patient already exhibited a rash at the time of diagnosis. He later developed difficulty with oral intake and became lethargic. Upon visiting the emergency room, he presented with erythema with purple tints on the trunk and extremities, including palms and soles. Laboratory tests revealed acute kidney injury and hyperkalemia. Suspecting prerenal acute kidney injury due to inadequate oral intake during COVID-19 treatment, we initiated rehydration therapy. The rash was initially attributed to COVID-19, but dermatological examination suggested Japanese spotted fever based on its distribution on the palms and soles, which is atypical for COVID-19. Tick bites were observed on the right thigh, prompting initiation of minocycline. A subsequent polymerase chain reaction (PCR) test later confirmed Japanese spotted fever. The patient deteriorated, experiencing cardiac arrest. He required intensive care but recovered and was transferred to a convalescent rehabilitation hospital. This case highlights the potential for overlooking Japanese spotted fever due to an initial diagnosis of COVID-19. Recognition of distinct rash characteristics led to the correct diagnosis. A thorough physical examination remains crucial, even when a COVID-19 diagnosis has already been made. This article was previously presented as a meeting abstract at the 51st Annual Meeting of the Japanese Society of Intensive Care Medicine on March 14, 2024.