During a recent survey a small population of Quadrula mitchelli (Simpson, 1895), a species thought to have been extinct, was discovered in Texas. In total, 7 live individuals were collected from the Guadalupe River near Gonzales, Gonzales County, Texas. Our finding represents the only known population for this species in Texas and the first record of live specimens in over 30 y, which is significant because this species is currently under review for protection under the Endangered Species Act.