Endometriosis is characterized by the presence of endometrial glands and stroma outside the uterine cavity. Appendiceal endometriosis, which is very rare, may have nonspecific presentation such as chronic pelvic pain, but sometimes it can masquerade clinically as acute appendicitis. Also appendiceal diverticulum may be congenital or acquired and is an infrequently encountered lesion. They are often asymptomatic but when diverticulitis or perforation develops, it may clinically mimic acute abdomen of acute suppurative appendicitis. Herein we report a case with a unique combination of appendiceal diverticulosis and endometriosis in a 39-year-old woman that was diagnosed preoperatively as acute appendicitis.