Introduction. Cesarean scar endometriosis (CSE) is a rare form of endometriosis that occurs due to previous surgical scars from obstetrical or gynecological procedures. The incidence of scar endometriosis after cesarean section is reported to be 0,03-0,45%, and it may cause long-term discomfort and cyclic lower abdominal pain. Case presentation. A 43-years-old multiparous woman came to our hospital complaining of a painful lump in the post-operative scar projection after a cesarean section with approximate sizes of 60x70 mm, which appeared 7 years ago but has increased significantly in the last year. Ultrasounds findings show a solid heterogeneous mass in hypogastric region extending from the lower region of the umbilicus to the projection of post-operative scar on the abdominal wall, immediately posterior to the subcutaneous adipose tissue in the projection of the muscle plane on the midline, measured 80x90x50x20 mm with moderate neovascularization in the interior. In February 2022, was performed mass resection, intraoperatively a solid infiltrate was detected in the aponeurosis, which was separated from the subcutaneous tissue, muscle, and peritoneum. Histological examination confirms fibromuscular tissue fragments with endometriosis outbreaks. Discussion. Abdominal wall endometriosis is largely related to the previous history of surgery, especially cesarean section and early hysterectomy. There is a combination of theories that best explains the pathogenesis of abdominal wall endometriosis: direct implantation during a surgical procedure on the endometrium or transportation to a cesarean section scar via lymphatic or hematogenous routes. The tissue implants either proliferate under the same hormonal stimulation as the endometrium in the uterus or induce metaplasia of the surrounding fascial tissue to form an endometrioma. Scar endometriosis may occur months and even years after surgery, and initially can be asymptomatic. Medical therapy is generally ineffective, and surgical resection of the scar endometrioma remains the mainstay of treatment. Because of the possible recurrence and malignant degeneration of this disease, in our case, there was performed a large surgical excision, with subsequent tissue reconstruction. Conclusion. Scar endometriosis is a rare disorder in which both stromal tissue and functional endometrial glands are seen outside the uterine cavity. It should be suspected in any female patient with a lump in the surgical scar, which becomes more painful and swollen during the menstrual period.