Mnuchin also served as the Trump campaign's finance chairman.
While the pick has been expected, it might come as a surprise to some of Trump's supporters who liked the president-elect's populist messaging and attacks on Hillary Clinton's ties to Wall Street.
Mnuchin spent 17 years at Goldman Sachs before leaving the bank, eventually co-founding hedge fund Dune Capital Management, which has financed numerous films.
Dune Capital has also done several real estate deals with Trump.
Trump even sued Dune Capital in 2008, according to Bloomberg.
The Senate will need to confirm Mnuchin, and pointed questions about at least one of his ventures will likely come up.
Mnuchin also served as chairman of Relativity Media, but he stepped down shortly before it filed for bankruptcy, according to Variety.