Twin pregnancy with complete hydatiform mole and coexisting viable fetus is a rare obstetrical phenomenon that may be difficult to diagnose on ultrasound and differentiate from abnormal placentation. Our goal is to describe how to make this diagnosis early and coordinate care and counseling, as the management remains controversial. A 27yo G7P3033 presented at17-weeks with vaginal bleeding. The diagnosis at an outside hospital was placenta previa with suspicion for a placenta accreta. A GE Voluson E8 (Milwaukee WI) transabdominal and transvaginal US with color Doppler revealed a structurally normal appearing fetus with cord insertion into a normal appearing placenta; a second placenta was noted to have a multicystic appearance with increased vascularity and lacunae. Serum-hCG of 1,000,000 and subclinical hyperthyroidism, with a normal CBC, CMP, Uric Acid, LDH, and TSH were noted. A chest X-ray revealed bilateral nodular densities. She was counseled on concern for a concomitant mole with a coexisting fetus (CMCF). A chest CT showed multiple well-circumscribed pulmonary nodules and enlarged axillary lymph nodes compatible with metastatic disease. A CT of the abdomen and pelvis revealed an enlarged uterus with hydatiform mole verses invasive disease with no signs of abdominal or pelvic metastasis. Brain and orbital MRI were negative. Maternal Fetal Medicine, Family Planning, and Gynecology Oncology specialists counseled the patient. She underwent a gravid hysterectomy. The pathology confirmed an invasive complete hydatiform mole, non-dysmorphic fetus with normal placenta, and placenta accreta. The patient is currently receiving Methotrexate for Stage III Gestational Trophoblastic Disease. Follow-up will be presented. Twin pregnancy with complete hydatiform mole and coexisting viable fetus is rare and it may pose significant maternal risks, with a small chance of delivering a viable fetus. This case was complicated by gestational trophoblastic disease with pulmonary metastases; the pregnancy was terminated in order to initiate maternal treatment.