He was admitted to the Michigan Bar in 1968 and commenced practice in Detroit.
He was elected to Michigan House of Representatives in 1970 and was reelected in 1972, from a district in Detroit.

In 1974, Martha W. Griffiths, Democratic incumbent for Michigan's 17th District to the United States House of Representatives was not a candidate for renomination.
Brodhead won nomination as the Democratic candidate and was elected to the Ninety-fourth and to the three succeeding Congresses, serving from January 3, 1975 to January 3, 1983.
While in Congress, Brodhead served on the House Ways and Means Committee and on the Budget Committee.
Brodhead also served as Chair of the Democratic Study Group which was then the liberal caucus in the House.
He was admitted to the Michigan Bar in 1968 and commenced practice in Detroit. He was elected to Michigan House of Representatives in 1970 and was reelected in 1972, from a district in Detroit.
In 1974, Martha W. Griffiths, Democratic incumbent for Michigan's 17th District to the United States House of Representatives was not a candidate for renomination. Brodhead won nomination as the Democratic candidate and was elected to the Ninety-fourth and to the three succeeding Congresses, serving from January 3, 1975 to January 3, 1983. While in Congress, Brodhead served on the House Ways and Means Committee and on the Budget Committee. Brodhead also served as Chair of the Democratic Study Group which was then the liberal caucus in the House.
William M. Brodhead