A 6-month-old girl with active human cytomegalovirus (HCMV) infection developed Reye's syndrome after vaccination. She suffered from uncommon complications of HCMV infection, including Coombs-negative hemolytic anemia and cardiac injury, but recovered after the appropriate treatment with prompt ganciclovir and symptomatic support. However, the patient died later as a result of a viral upper respiratory tract infection, which aggravated the primary disease. This case suggests that HCMV infection might be a causative agent of Reye's syndrome. J. Med. Virol. 85:490–492, 2013. © 2012 Wiley Periodicals, Inc.