Chaetomium species are rare causes of infections in immunocompetent patients. These include classic allergy symptoms such as wheezing, runny eyes, and coughing, onychomycosis and sinusitis. Chaetomium species on the other hand can cause serious and fatal infections in immunocompromised patients and intravenous drug users. These include empyema, pneumonia, and fatal disseminated cerebral disease. A 17-year-old girl presented with weight loss, abdominal distension and pain. Initial clinical, radiological and laparoscopy features were suggestive of tuberculous peritonitis, and was managed accordingly, with some evidence of improvement. However, fungal culture eventually confirmed the diagnosis of Chaetomium peritonitis. This report describes the first case of Chaetomium peritonitis infection simulating tuberculous peritonitis in an immunocompetent patient.