Mesenteric fibromatosis (MF) is a locally aggressive proliferative spindle cell lesion of the mesentery. A 34-year-old male presented with increasing abdominal pain and constipation. On workup, patient was found to have a large pelvic mass on CT A/P concerning for cancer. The patient underwent surgical excision of >15 cm intra-abdominal tumor along with adherent small bowel section. Histology of the tumor showed a spindle cell lesion consistent with MF. Previous reports have shown association of MF with Gardner syndrome and familial adenomatous polyposis. We present the first reported case of MF in a patient with previous neuroblastoma.