Nogales is a city in and the county seat of Santa Cruz County, Arizona. The population was 20,837 at the 2010 census and estimated 20,103 in 2019. Nogales forms part of the larger Tucson–Nogales combined statistical area, with a total population of 1,027,683 as of the 2010 Census. Nogales forms Arizona's largest transborder agglomeration with its adjacent, much larger twin Nogales, Sonora, across the Mexican border.