Brown, who served in the Senate from 2010 to 2012 before losing his seat to Sen. Elizabeth Warren (D-Mass.), announced the move on Wednesday.
"I am honored to have the opportunity to contribute to Kadant and learn more about the challenges of an international business," Brown said in a statement. "Kadant has been on the forefront of designing and manufacturing equipment to recycle and produce paper for decades. I look forward to sharing my knowledge and experiences and contributing to the future direction and growth of this global leader."
Brown is finishing out the term of a former member of the board who stepped down in order to retire, according to Kadant spokesman Thomas O'Brien.
The company is based in Westford, Mass. Besides Brown, former Sen. Paul Tsongas (D-Mass.) also served on Kadant's board.