Richardson will join Obama at a news conference in Chicago for the announcement, a Democratic official told The Associated Press.
Richardson, an early and outspoken supporter of Obama during the Democratic primary this year, reportedly was disappointed that the secretary of state job went to Sen. Hillary Clinton. But Obama convinced him he would play a major role as commerce secretary, and help him promote key legislation in Congress.
Richardson was energy secretary and United Nations ambassador in President Clinton's administration. He sought the Democratic presidential nomination this year, but eventually dropped out and endorsed Obama.
He is one of the nation's most prominent Hispanic politicians, and was in the U.S. House before joining Clinton's Cabinet.
Obama named his economic team last week and his national security team on Monday, filling half of his Cabinet.