Pelvic masses occur in up to 20% of women throughout their lifetime. These masses represent a spectrum of gynecologic and nongynecologic conditions. Adnexal masses—found in the fallopian tubes, ovaries, and surrounding areas—are mostly benign. Evaluation includes assessment for symptoms that may suggest malignancy, such as abdominal pain, abdominal bloating, and early satiety. A family history of ovarian, breast, or certain heritable syndromes increases the risk of malignancy. For women of reproductive age, ectopic pregnancies must be considered; a beta human chorionic gonadotropin level should be obtained. Transvaginal ultrasonography is the imaging test of choice for evaluating adnexal masses for size and complexity. Adnexal cysts that are greater than 10 cm, contain solid components, or have high color flow on Doppler ultrasonography are high risk for malignancy. Further imaging, if warranted, should be completed with computed tomography or magnetic resonance imaging, particularly if there is concern for disease outside the ovary. Multimodal assessment tools that use ultrasonography and biomarkers, such as the risk of malignancy index, are useful in the diagnosis and exclusion of malignant causes. Asymptomatic masses that are determined to be benign may be observed and managed expectantly. In symptomatic or emergent cases, such as ectopic pregnancy or ovarian torsion, a gynecologist should be consulted. In any adnexal mass with high risk for malignancy, a consultation with gynecologic oncology is indicated.