We report a case of a 32-year-old woman with episodic right lower quadrant abdominal pain. With the diagnosis of either acute appendicitis or tuba-ovarian abscess, she was treated with antibiotics, which successfully relieved the pain and the inflammatory findings. She repeated the clinical condition a few times and antibiotics worked each time. In a year, her subjective symptoms became milder, however, a giant pelvic cyst appeared. She had an exploratory laparotomy to confirm this diagnosis. Histopathological studies revealed hiated appendiceal mucosa through the muscular layer associated with chronic inflammation and marked fibrosis. Gynecological disorders such as endometriosis or lutein cyst rupture was denied. These findings represent appendiceal diverticulitis. We discuss the clinical features of the disease and its relation with the pelvic pseudocyst.