He served in the U.S. Department of Justice as Assistant Attorney General of the Office of Legal Counsel in 1961–1962 and as Deputy Attorney General appointed by President John F. Kennedy in 1962. After the assassination of President Kennedy, Katzenbach continued to serve with the Johnson administration On February 11th, 1965 President Johnson appointed Katzenbach the 65th Attorney General of the United States, and he held the office until October 2, 1966. He then served as Under Secretary of State from 1966 to 1969.