Bispedømmet Austin omfatter områdene Bastrop County, Bell County, Blanco County, Brazos County, Burleson County, Burnet County, Caldwell County, Coryell County, Falls County, Hamilton County, Hays County, Lampasas County, Lee County, Limestone County, Llano County, Mason County, McLennan County, Milam County, Mills County, Robertson County, San Saba County, Travis County, Washington County og Williamson County.