Pelvic actinomycosis with multiple fistular formation is rarely reported in the literature. We herein present a case of pelvic actinomycosis with sigmoid colo-ileovesical fistulae in a 36-year-old intrauterine device (IUD) user. She was admitted to the hospital because of general malaise, weight loss and bilateral palpable adnexal masses. Sonography showed bilateral adnexal masses which contained many echolucent spots. A barium enema examination revealed sigmoid colo-ileo-vesical fistulae. A computed tomographic scan showed bilateral cystic adnexal masses, bilateral hydronephrosis and hydroureter. Preoperatively, pelvic malignancy was suspected. An exploratory laparotomy was performed. Bilateral tubo-ovarian abscesses with extensive adhesions were found. Pathologic examination of the operative specimen revealed pelvic actinomycosis. The patient was treated with penicillin for 14 weeks and had a stable clinical course.