A 64-year-old Japanese man with multiple myeloma was admitted to our institute due to fever and hypotension. He had received multiple courses of chemotherapy just before his febrile episode. Blood culturing detected Morganella morganii. At the time of the diagnosis, his laboratory findings revealed massive rhabdomyolysis with a significantly increased creatinine kinase level (CK; 3,582 U/L); 98.8% of which corresponded to the CK-MB isotype. We diagnosed the patient with sepsis caused by M. morganii, complicated with severe rhabdomyolysis. He died of multi-organ failure 2 days later. Clinicians should closely observe patients with possible systemic infection-associated rhabdomyolysis.