Lipomas are benign, usually asymptomatic, tumours and pelvic lipomas are extremely rare. We describe the case of a giant pelvic lipoma causing obstructive uropathy to a 66-year-old morbidly obese female treated in the 4th Surgical Department of the Medical School of Aristotle University of Thessaloniki in General Hospital "G. Papanikolaou" in March 2016. The patient presented with a history of nocturia and frequent daytime urination for 1 year. Her medical history included diffuse lipomatosis. Computer tomography revealed a giant pelvic mass which lead to left side hydronephrosis, hydrouterer and a pear-shaped bladder, with the differential diagnosis including pelvic lipoma or liposarcoma. An ultrasound guided biopsy excluded the diagnosis of liposarcoma. The patient was submitted to laparoscopic resection of the pelvic lipoma, with complete remission of urinary symptoms. The key-point is to consider the possibility that the pelvic mass is a well-differentiated liposarcoma and to manage it adequately and thus, we recommend intact excision of the mass through a wound protector, and extreme caution to avoid any rupture of the capsule.