Mnuchin said the decision would be based on how to design the currency in a way that prevents counterfeiting, rather than whose portrait was on the bill.
"Ultimately we will be looking at this issue," Mnuchin said in a CNBC interview. "It's not something I'm focused on at the moment."
Mnuchin added that "the issues of why we change it will be primarily related to what we need to do for security purposes."
President Barack Obama and his then-Treasury Secretary Jacob Lew proposed last year to take President Andrew Jackson's image off the $20 bill and replace it with Harriet Tubman. Tubman, a famous abolitionist who helped many enslaved people escape, would be the first woman on a U.S. bill and she would also be the first African American on a U.S. bill.
Under Lew's plan, Tubman's image would be on the front of the $20 bill and President Jackson's image would appear on the reverse of the currency.
The process was supposed to take several years.
President Donald Trump has said he is very fond of President Jackson, at times remarking that his election was reminiscent of the populist campaign that brought Jackson into power in 1829. Trump has a portrait of Jackson on the wall in the Oval Office.
Last year, in an interview with NBC, Trump said Tubman was "fantastic" but said putting her on the $20 bill was an example of "pure political correctness."
"Well, Andrew Jackson had a great history, and I think it's very rough when you take somebody off the bill," Trump said last year. "I think Harriet Tubman is fantastic, but I would love to leave Andrew Jackson or see if we can maybe come up with another denomination."