Introduction Mesenteric fibromatosis-desmoid tumor of mesentery is a rare benign soft tissue tumor of mesentery. On CT, it mimics gastrointestinal stromal tumor (GIST). Case Report A 44-year-old female with small intestinal mass, preoperatively diagnosed radiologically and pathologically as GIST. Conclusion Mesenteric fibromatosis is a rare tumor often mistaken for GIST. Histopathology and immunohistochemistry is the key as management of both the tumors differs.