Introduction: Spontaneous bacterial peritonitis (SBP) is a fatal infection in patients. It often happens in patients with cirrhosis, cancer or diabetes, and is caused mostly by Enterobacteriaceae. Here we report a rare case of SBP caused by Campylobacter Coli (C coli) infection, which was identified promptly by the matrix assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) and received adequate therapy sooner after. Patient concerns: In the present study, we reported a 46-year-old male with alcoholic liver cirrhosis (Child-Pugh class C) and type 2 diabetes mellitus presented with a 1-day history of fever and abdominal pain. Diagnosis: Based on the clinical examinations, the patient was diagnosed with SBP and the pathogen was quickly identified as C coli by the matrix assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS), a rare causative pathogen of SBP. Interventions: The patient received a 10-day antibiotic treatment with Ciprofloxacin 400 mg every 12 hours, and recovered successfully. Outcomes: The patient had a successful treatment outcome. Conclusion: The study demonstrated a new possible infectious cause of SBP by C Coli, which was rarely seen in liver cirrhosis but mostly found in immunocompromised patients. Thus, it might raise an idea of microorganism screening of broader types that might also induce SBP for immunocompromised patients.