Retroperitoneal leiomyoma is a rare benign tumor of the retroperitoneum. We report a clinical case of a 43-year-old patient, who suffered from back pain and weight loss. Imaging revealed a retroperitoneal mass, then the patient had a total excision of the tumor. Histological examination of the surgical specimen concluded to retroperitoneal leiomyoma. The evolution was good without recurrence after 12 months.