Acute angle-closure glaucoma is a clinical phenomenon with potentially devastating consequences, including permanent blindness, if not promptly diagnosed and treated. We describe an unusual case of acute angle-closure glaucoma, leading to the detection of a uveal melanoma, a potentially life-threatening cause of glaucoma. Bedside ultrasonography of the eye was used to assist in the diagnosis, providing rapidly available diagnostic information about the size and extent of the tumor. Because acute angle-closure glaucoma may occur due to multiple etiologies, this case highlights the importance of uncovering occult causes of increased intraocular pressure.