Endometriosis, firstly described by Rokitansky in 1860, is characterized by presence of endometrial glands and/or stroma outside the uterine cavity. Estimated prevalence is about 10–15% in women of reproductive age group. Gastrointestinal involvement is known to occur in 3–37% of the cases with recto–sigmoid being the most common site of involvement. Endometriosis involving intestinal mucosa is relatively uncommon. It poses a diagnostic challenge for clinicians and pathologists. In case of misdiagnosis, any pathologists should be aware of intestinal endometriosis for each female‘s colorectal biopsy, especially for that morphology not typical for primary adenocarcinoma. Reading slides carefully combined with a panel of immunomarkers would solve the pitfall.