Citrobacter species is a gram-negative bacilli that can cause opportunistic infections in immunocompromised hosts. Citrobacter braakii refers to the genomospecies 6 of the Citrobacter freundii complex. There are no detailed studies on infections caused by this newly identified specific genetic species in Korea. We herein report a case of a patient with hepatocellular carcinoma who, after undergoing transcatheter arterial chemoembolization, developed biloma which later progressed to C.braakii sepsis and did not respond to treatment. To our knowledge, this is the first reported case in Korea on C. braakii infection resulting in septic shock in a patient with malignancy in Korea.