Background: Endometriosis is a prevalent benign, inflammatory, estrogen-dependent disease that affects between 1% to 11.5% of women. Deep endometriosis is one of the three types of endometriosis. Described as “deeply infiltrating endometriosis" or “adenomyosis externa," and it is characterized histopathologically as endometrial glands and stroma penetrating adjacent fibromuscular tissue, obliterating and substituting connective tissue septa. Objective: The present work aimed to report a case of endometriotic of the iliacus muscle and psoas muscle. Mention the place and time of the study. Conclusion: Deep endometriosis is rare to infiltrate the retropsoas area (iliacus, iliopsoas) and the diagnosis can be difficult, therefore a comprehensive patient assessment is necessary for adequate treatment. The use of appropriate imaging techniques, such as MRI and CT scans, is essential to show the lesions.