Sarcina ventriculi is a gram-positive anaerobic coccus that commonly associated with various gastrointestinal diseases. Here, we report a complete case of bloodstream infection caused by Sarcina ventriculi for the first time. A 60-year-old male patient diagnosed with sigmoid colon adenocarcinoma who had undergone multiple chemotherapy and radiotherapy. The patient underwent blood culture sampling due to fever and the pathogen identified as Sarcina ventriculi through 16S rRNA sequencing analysis. Sarcina ventriculi has a unique arrangement and cell wall structure, which can easily be mistaken for a fungus. This case reveals the difficulties in the diagnosis and treatment of Sarcina ventriculi infection. It can be served as a reference for clinicians and microbiologists faced with similar diagnostic and treatment challenges in the future. Meanwhile, we call for increased attention to Sarcina ventriculi which may also be the late complication of gastrointestinal malignancies.