Background: Different Clostridial organisms, commensal in gut flora, can cause blood stream infections, especially in underlying malignant disease. Here, we are presenting first case report of Clostridium hastiforme sepsis in a patient with rectal malignant disease. Methods: Case report and review of pertinent English-language literature. Result: A 49-y-old female with known rectal malignant disease was admitted for sepsis with sudden onset sharp rectal pain, fever, leukocytosis, and lactic acidosis. The patient was undergoing palliative chemotherapy. Computed tomography (CT) revealed large rectal carcinoma with central necrosis and distant metastasis. She was started empirically with intravenous vancomycin and piperacillin-tazobactam. Blood culture grew gramvariable rods only in anaerobic bottles, which was subsequently identified as C. hastiforme. Antimicrobials were changed to metronidazole. The patient improved clinically and was discharged subsequently. Conclusions: The report emphasizes the importance of rare Clostridial organisms to cause sepsis in patients with underlying gastrointestinal malignant disease. Patients with this condition are usually gravely ill and the infection can be easily missed if anaerobic culture is not routinely ordered.