Endometriosis of the rectus abdominis muscle is an extremely rare form of extrapelvic localization of the disease. It is usually iatrogenic and develops after caesarean section or gynecological surgery. Preoperative diagnosis is very difficult and a challenge for gynecologists and surgeons; thus, the diagnosis is histological. The treatment of choice consists of wide local excision of the lesion on healthy margins. We cite a case of isolated endometriosis in the rectus abdominis muscles in a 46-year-old patient with a previous caesarean section, the diagnosis of which was made randomly when performing abdominal total hysterectomy for the treatment of chronic pelvic pain. Histological examination of the surgical specimen confirmed the diagnosis. Simultaneously, the surgical specimen of the uterus and ovaries was free of endometriosis. Postoperatively, the patient mentioned discharge of her symptoms. No further therapeutic intervention was deemed necessary, as it was considered that a complete resection of the endometrial tissue implantation from the muscles of abdominal wall was performed. The present case report lay emphasis on the significant difficulties involved in the preoperative diagnosis of endometriosis of the rectus abdominis muscle. Concurrently, it is pointed out that, despite its rarity, individual extrapelvic endometriosis located in the rectus abdominis muscle should be included among other pathological entities in the differential diagnosis of chronic pelvic pain in women of reproductive age, who gave birth by caesarean section or underwent gynecological surgery with abdominal or laparoscopic access.