Background: Basidiobolus ranarum is a fungus that usually causes subcutaneous infection. Medical literature rarely report gastrointestinal involvement, especially in tropical climate areas.Case Report: Here we report a case of gastrointestinal basidiomycosis in an immunocompetent 43-year-old man from south of Iran who presented with abdominal pain, loss of appetite, and nausea. He had history of previous laparotomy 10 years ago, because of perforated peptic ulcer. He underwent an exploratory laparotomy. We found a mass in ascending colon; so, right hemicolectomy were done. Histologic founding were amazing. Eosinophilic sheath surrounding hyphae-like structures was seen. The diagnosis of basidiomycosis was established, so we prescribed antifungal agents for the patient. He expired 6 months later according to disseminated disease.Conclusions: Gastrointestinal basidiomycosis is a rare and invasive fungal infection that imitates malignant tumors, inflammatory bowel disease, or even phlegmon of appendicitis. Diagnosis of gastrointestinal basidiomycosis needs a high index of suspicion. The physicians should be aware of this disease as differential diagnosis in tropical areas. Surgical resection and prolonged antifungal therapy is recommended, but in some cases, the disease may spread and cause death
