The differential diagnosis for women presenting with chronic genitourinary symptoms is extensive. Urethral diverticulum has long been thought to be responsible for these symptoms in some women. Although the etiology of urethral diverticulum in women is unclear, a number of different theories have been advanced for the formation of diverticula including either a congenital or acquired etiology. A few cases of acquired urethral diverticulum have been reported that resulted from endometriosis; however, there have been no such cases reported in Korea. We recently treated a 58-year-old woman who presented with complaints of a protruding mass through the vaginal wall. A diagnosis of urethral diverticulum secondary to endometriosis was finally made. The patient underwent surgical repair. Here we report this case and review the medical literature.