Aeromonas hydrophila (A. hydrophila) occasionally causes necrotizing fasciitis (NF) and sepsis in immunocompromised hosts. NF is associated with high mortality. In cases of septic shock due to A. hydrophila, mortality is nearly 100%. Our 47-year-old male patient was diagnosed with NF and septic shock due to A. hydrophila. He had not been exposed to fresh or slightly salty water, which is where the bacterium is typically found, so its origin in this case is unclear. This is the first known case in which the patient was able to be completely cured without amputation. NF was suspected from his sepsis, medical history including alcoholic cirrhosis, and a severely poor general condition, but his skin lesions were mild. We promptly made an exploratory incision and debrided his legs. NF could then be diagnosed. At an early stage, A. hydrophila was recognized as a possible pathogen of NF because of the patient's medical background and the Gram stain findings of intraoperative exudate. Minocycline in addition to carbapenem and vancomycin plus clindamycin were administered as empiric therapy. When A. hydrophila was detected in the blood culture, ciprofloxacin was administered as definitive therapy. Successful treatment of NF requires early diagnosis, prompt debridement from onset and adequate empirical antibiotic therapy.