In 1958 he moved to Washington, D.C., to serve as the United States Assistant Attorney General of the Office of Legal Counsel at the United States Department of Justice (1958–1959), and Assistant Attorney General of the Criminal Division (1959–1961).

He returned to private practice in Texas (1961–1963), before moving on to become the General counsel and secretary of Kennecott Copper Corporation (1963–1970), during which he was also a member of the Advisory Panel on International Law for the legal adviser at the United States Department of State (1969–1973).

Wilkey was nominated by President Richard Nixon on February 16, 1970, for the seat vacated by Judge Warren E. Burger on the United States Court of Appeals for the District of Columbia Circuit.

[2] He assumed senior status on December 6, 1984, and his judicial service ended November 8, 1985, when he retired and went to Cambridge University as a visiting fellow of Wolfson College.

[5] In 1992 United States Attorney General William P. Barr appointed him to determine whether federal criminal violations had taken place in the House banking scandal.