Pete Buttigieg is to succeed Elaine Chao as US transportation secretary.
In a TV address, president-elect Joe Biden called him "a new voice with new ideas".
He described the US Department of Transportation as having "a critical mission with critical responsibilities".
"We need someone who knows how to work with state, local and federal agencies."
Biden outlined infrastructure challenges such as roads and bridges in poor repair and talked about the importance of clean energy in transport.
He said that work to combat climate change would create good jobs and that a better transportation system would increase equity.
Buttigieg would be "at the intersection of some of our most ambitious plans to build back better", Biden said.
Buttigieg himself said the new administration had a "historic opportunity".
The former mayor of South Bend, Indiana, Buttigieg had his own tilt at the Democratic nomination for president, before pulling out and endorsing Biden.
He will take up his new post when Biden is sworn in on 20 January.
