The gastric bypass is a good option in the therapy of morbid obesity. Nevertheless, it must be considered the rare condition as occurred in a patient with previous abdominal surgery with Situs Inversus Totalis. A 24 year-old male patient with body mass index of 40 Kg/ m², multiple dietary failures, and arterial hypertension as co-morbidities, with a anterior paramedial right incision due to a previous appendicectomy (8 years ago).With a indication for bariatric surgery, was performed Roux-en-Y gastric bypass by laparoscopic procedure, with previous planning of Situs Inversus Totalis.