In 1932, he obtained his law degree from the University of Arizona. He served on the Arizona Colorado River Commission and was appointed to the Arizona Board of Regents in 1941. He was Arizona's Attorney General from 1948 to 1949. He was appointed to the Arizona Supreme Court in 1949 and served until 1953.
From 1966 until his death in 1986, DeConcini worked as attorney for with DeConcini McDonald Brammer Yetwin & Lacy in Tucson. He died from heart disease in a Tucson hospital and is buried in Holy Hope Cemetery.