In 1965, Kennedy ran for Wayne County Circuit Court judge and lost by less than 100 votes. The next year, she ran again and won.
In 1970, Kennedy was appointed by Richard Nixon to the U.S. District Court for the Eastern District of Michigan.
In 1977, Kennedy became the chief judge on that court, becoming the first woman to serve as chief judge of a U.S. district court.
Jimmy Carter elevated Kennedy to the U.S. Court of Appeals for the Sixth Circuit in 1979.