Leavitt, who left her previous position at the White House in August after becoming a mother for the second time earlier this year, is expected to appear as a commentator on several of the channel's television programs, the newspaper writes.
Fox News has historically had close ties to Trump, who has defended the channel and some of its most high-profile employees.
Karoline Leavitt has been described as one of Trump's closest aides. At press conferences, she has defended the president and criticized various media outlets. When she was hired, she was the youngest-ever White House press secretary.
