Primary mesenteric Liposarcoma is a rare neoplasm and only few documented cases are there in literature that too in adults. We report a case of giant primary mesenteric Liposarcoma in an adolescent male. Our patient is a 17 yrs old male who presented with gradual abdominal distension and was found to have huge multilobated and heterogeneous abdominal tumor arising from transverse mesocolon on imaging. The excised tumor weighed 19 kg and was reported as well differentiated Liposarcoma (WDLPS) on histomorphology. Atypical Lipomatous Tumor and WDLPS are synonyms describing lesions that are identical morphologically, karyotypically and in terms of biological potential. In deep visceral sites where wide excision margin are difficult to attain, the term WDLPS is preferred. Myxoid Liposarcoma is the most common variant of LPS seen in children and young adults with lower extremities being commonest site of occurrence. Our case is unique in rarity of lesion, its dimensions, location and uncommon histomorphology for age.