He served in the United States Army during World War II, and was thereafter prosecutor for Camden County, New Jersey from 1948 to 1958.
[1] On July 6, 1962, Cohen was nominated by President John F. Kennedy to a seat on the United States District Court for the District of New Jersey vacated by Judge Richard Hartshorne.
He served as Chief Judge from 1973 to 1974, assuming senior status on September 11, 1974.
Cohen served in that capacity until his death, on January 7, 1991, in Philadelphia.
[1] The Mitchell H. Cohen United States Courthouse in Camden was dedicated in 1994.