In 1914 he married Louisa Lee, a granddaughter of John D. Lee and Jacob Hamblin. They would later have six children.
He passed the Arizona Bar exam in 1922, and was admitted to the bar, without having earned a law degree (a common practice in those days). Later that year he succeeded his father as stake president of the St. Johns Stake, a position he held until 1945.
In 1922, he lost a bid to be elected as clerk to the Arizona Superior Court.[where?] He was defeated by his older brother John Hunt Udall.
In 1946 he was elected to the Arizona Supreme Court, and remained a Justice of that court from 1947 until his death. In 1948 Udall wrote the majority opinion of the Arizona State Supreme Court granting Native Americans living on reservations the right to vote.[2] From 1951 to 1952 and 1957–1958 he served as the chief justice of that court.[3]