A multiparous woman in her 40s had advanced peritoneal adhesions and frozen pelvis from 3 previous surgeries. Endometrial ovarian cysts also remained. After the last surgery, imaging showed cysts with a septum and enhanced moieties in the Douglas pouch. Highly invasive surgery was anticipated, and the patient underwent a transvaginal ultrasound-guided core needle biopsy(TVCNB, 16-gauge needle)with full awareness of the risks involved. The histopathological diagnosis was adenocarcinoma. We inserted a ureteral stent and performed an S-shaped colon resection and standard ovarian cancer surgery after preoperative chemotherapy. TVCNB in this case was less invasive and easier to perform than other exploratory procedures, and has a low risk of iatrogenic intraperitoneal dissemination even if the tumor is malignant. Chemotherapy can be administered before surgery if malignancy is detected. In summary, TVCNB is a useful alternative method for conducting exploratory operations.