Primary sclerosing cholangitis (PSC) is a rare, chronic, and progressive disease of the liver characterized by cholestasis due to multifocal bile duct strictures. PSC can lead to liver fibrosis, and in 10-20% of cases, it leads to cholangiocarcinoma and end-stage liver disease. However, the pathogenesis of the disease is not clearly understood. For the diagnosis of PSC, both imaging and liver biopsy can be used. No medical treatment has managed to prevent the progression of the disease. Consequently, in the case of late-stage disease, liver transplantation is considered the best treatment option. PSC may lead to different complications including bacterial cholangitis, cholangiocarcinoma, and cirrhosis. Nevertheless, to our knowledge, there are no reports of granulomatous peritonitis secondary to PSC. Granulomatous peritonitis may be a result of infectious, malignant, and idiopathic inflammatory diseases. It is also considered a rare postoperative complication, due to cornstarch from surgical glove powder, in laparoscopic procedures. Here, we report the case of a 39-year-old male patient with PSC, in which cholangiocarcinoma and peritoneal carcinomatosis were clinically suspected. Despite that, histological findings and staining methods of the surgically removed peritoneal masses demonstrated granulomatous peritonitis.