Mesenteric fibromatosis is a rare benign nonmetastatic neoplasm that appears as a sporadic lesion or occurs in patients with familial polyposis, while chylous ascites associated with aggressive mesenteric fibromatosis during pregnancy has never been reported thus far. Here we present the case of a 28-year old pregnant woman, in whom an aggressive mesenteric fibromatosis with chylous ascites was detected, involving the jejunum, superior mesenteric artery (SMA) and superior mesenteric vein (SMV) and pancreas. One year after a successful surgical excision, the patient had no signs of recurrence. The authors report the case for its rarity and emphasize on combining clinicopathological, radiological and immunohistochemistry analysis for management of the disease.