A top transition source told NBC News that he could be named as soon as Wednesday.
Mnuchin, who served as finance chairman for Trump's presidential campaign, was last the chairman of Dune Capital Management. Mnuchin's firm's Hollywood financing has helped to fund James Cameron's "Avatar," among other blockbusters. He previously spent 17 years at Goldman Sachs, worked at Soros Fund Management and co-founded OneWest Bank Group.
The possible appointment of Mnuchin, an alumnus of one of the world's most powerful financial institutions, seems to clash with Trump's populist campaign rhetoric and pledge to be the "voice" for downtrodden blue-collar workers. Mnuchin would take the helm of a Treasury that could take a starkly different approach than the department did under the Obama administration on taxes, trade and financial regulation.
It is not entirely clear how much Mnuchin's personal views align with the financial priorities Trump has outlined for his United States. Mnuchin, like Trump, donated heavily to Democratic candidates before this cycle. Like Trump, his economic standing has little in common with the economic populism that helped to propel Trump to the White House.
While serving as campaign finance chairman, Mnuchin also outlined some of the economic priorities of a possible Trump administration.
"We are very focused on lowering business taxes, making sure that U.S. corporations are competitive around the world, bringing back cash from all around the world that's sitting offshore and I think the American public is focused on that," Mnuchin told CNBC in August.
President-elect Trump has pledged to cut the U.S. corporate tax rate to 15 percent from more than 30 percent currently, saying it will encourage companies to keep their tax addresses in the United States. Obama's Treasury under Jack Lew has enacted rules to make it more difficult for companies to use inversions to get lower tax rates overseas.
Trump's administration will clash with Obama's on trade, as Trump wants to scrap the Trans-Pacific Partnership and Lew said earlier this year he hoped the Asian trade agreement could still be passed. In addition, Trump has trashed and pledged to repeal the Dodd-Frank financial reform act, which Obama's administration praises for helping to create what it calls a safer financial system.
Mnuchin was named Trump's campaign finance chairman in May. The campaign did not start seriously fundraising until June, much later than presidential candidates typically do.
Trump defeated Democrat Hillary Clinton while both raising and spending considerably less than his rival. Mnuchin helped to oversee a campaign that spent much less than Clinton on television advertising and payroll, benefiting from free media coverage and social media efforts.
— NBC News contributed to this report.