Borderline Brenner tumors represent quite a rare entity of ovarian tumors (about 2%) that develop from the surface ovarian epithelium. They are formed from papillary structures made of fibrovascular conjunctive axes covered by a transition epithelium, similar to the urinary bladder epithelium. According to the WHO classification, Brenner tumors present the following forms: benign, borderline and malignant. The benign ones are the most frequent, representing about 95%, the borderline represent about 5%, and the malignant ones less than 1%. We present the case of a 64-year patient who was diagnosed with right ovary cyst. The histopathological examination highlighted the presence of a borderline Brenner tumor at the same time with the cystic lesion, on the same ovary. The surgical treatment led to a complete cure of the patient, so that the yearly ultrasound reexamination did not trace the presence of any tumoral relapse.