Dempster was released and signed with the Chicago Cubs in 2004 where he played until 2012 when he was traded to the Texas Rangers. In 2013 he signed a two year $26.5 million contract with the Boston Red Sox. In February 2014 he announced that he would not pitch in 2014. Dempster worked as a starting and relief pitcher during his MLB career. He won his only World Series Championships with the Rex Sox in 2013. He was a two time All Star in 2000 and 2008 and won the Tip O’Neill Award in 2000. In April 2014 he became a studio color analyst for the MLB Network.