Tukwila is a suburban city in King County, Washington, United States, located immediately to the south of Seattle. The population was 21,7…Tukwila is a suburban city in King County, Washington, United States, located immediately to the south of Seattle. The population was 21,798 at the 2020 census. A large commercial center draws workers and consumers to the city daily; industry thrives with the confluence of rivers, freeways, railroads, and Seattle–Tacoma International Airport.