Endometriosis is a common gynaecological pathology characterized by the presence of endometrial tissue outside the uterine cavity, and the most frequent locations of endometriosis are ovaries and posterior compartment of the pelvis. In this paper we report the case of a rare bilateral endometriosis location of posas muscle diagnosed and treated in a 25-year-old patient. This is the third case of psoas endometriosis location reported, but the first one successfully treated by hormone estrogen-progestogen treatment alone. Psoas endometriosis is a rare location and the medical management in first line can be an alternative to surgery and provide optimal patient relief.