Arteriovenous malformations (AVMs) are abnormal vascular connections that can form in many anatomic locations. The adnexa are particularly rare sites of AVM formation and the symptomatology is heterogeneous. Herein we present a case of life-threatening adnexal AVM. A 21-year-old female presented with abdominal pain and syncope, her third such presentation within 10 days. Her history was significant for ectopic pregnancy six months prior. Diagnostic laparoscopy revealed intraperitoneal blood without active bleeding. Transabdominal pelvic ultrasound revealed a large amount of complicated pelvic fluid and increased right-adnexal vascularity. Interventional radiology performed an urgent uterine arteriogram revealing a right-adnexal AVM with supply from both the right uterine and right ovarian arteries. The AVM was subsequently embolized, resolving her symptoms. AVMs are exceedingly rare, often unconsidered causes of occult pelvic bleeding. Pelvic, and in particular, adnexal AVMs should be considered in females with idiopathic spontaneous hemoperitoneum.