Combined oral contraceptives (COCs) are the most frequently chosen treatment option in abnormal uterine bleeding, The COCs currently in use, containing small dosages of estrogen and progesterone, produce an arrest of endometrial glanduler proliferation during the first cycles. Also the combination of inactive glands, abortive secretion and thin blood vessels are characteristics of COCs therapy effect. Here we report a case describing heavy vaginal bleeding and the passing of a large sized piece of tissue due to the use of COCs. Although there are cases that report pseudodesidualized endometrium after taking medroxyprogesterone acetate (MPA) or levenorgestrel-releasing intrauterine system (LNG), COCs related any mass like huge pseudodecidual reaction has not been described in literature so far. In this case, pelvic imaging and endometrial sampling had not been performed prior to commencing medical therapy. However the use of out-patient techniques such as endometrial sampling and/or hysteroscopy is indicated in abnormal uterine bleeding cases to exclude other intrauterine pathology before starting any treatment options.