Tehran University of Medical Sciences Case Reports in Clinical Practice 2538-2683 6 6 2022 04 11 231 234 Seyedhadi Mirhashemi Department of General Surgery, Loghman Hakim Hospital, Shahid Beheshti University of Medical Sciences, Tehran, Iran. Manoochehr Ebrahimian Department of General Surgery, Loghman Hakim Hospital, Shahid Beheshti University of Medical Sciences, Tehran, Iran. Mehrnoosh Kialashaki Department of General Surgery, Loghman Hakim Hospital, Shahid Beheshti University of Medical Sciences, Tehran, Iran. Elena Jamali Department of Pathology, Loghman Hakim Hospital, Shahid Beheshti University of Medical Sciences, Tehran, Iran. 2021 01 03 2021 01 18 Endometriosis is among the most frequent causes of appendiceal intussusception. However, there are limited data about this condition. Still, clinical manifestations, diagnosis, and treatment are the same in almost all cases due to accidental implantation of endometrial tissue inside the appendiceal wall. Finally, the only choice of treatment is appendectomy. Here we describe a middle-aged woman with vague pelvic pain that underwent a laparoscopic cystectomy, and during surgery, we came across a mass-like appendix. The pathology report declared that some endometrial tissue inside the appendix confirms the diagnosis of appendiceal intussusception due to endometriosis. https://crcp.tums.ac.ir/index.php/crcp/article/view/448