Seagoville is a city in Dallas County, Texas, United States, and a suburb of Dallas. A small portion of Seagoville extends into Kaufman County. T…Seagoville is a city in Dallas County, Texas, United States, and a suburb of Dallas. A small portion of Seagoville extends into Kaufman County. The population was 18,446 at the 2020 census. The city is located along U.S. Highway 175, 10 miles from downtown Mesquite.