We report the case of a 26-year-old woman with a right auto-amputated adnexa and a free-floating mass in the pouch of Douglas using multimodal imaging studies including ultrasonography, computed tomography, and magnetic resonance imaging. The absence of an ovary and the evidence of an amorphous and potentially calcified mass, with no connection to the genital tract – in particular when it is found to be mobile – are the key imaging findings. Prospective diagnosis of adnexal auto-amputation could assist surgeons in patient management with a curative laparoscopy in symptomatic women, or potentially expectant management in young women who are asymptomatic or have unrelated symptoms.