Icahn, 80, will serve as Trump's special adviser on federal regulations reform. The role, though, is not an official government job.
"I'm involved with Donald where he wants me to be. I believe he respects my views and I think he listens to me," Icahn told The Wall Street Journal on Wednesday. "What Trump is trying to achieve is to show business in a lot of this country they aren't going to be ruined by absurd regulation by bureaucrats."
Trump said of Icahn: "He is not only a brilliant negotiator, but also someone who is innately able to predict the future especially having to do with finances and economies."
Icahn, who has a reported net worth of $16 billion, joins several other billionaires in Trump's administration: the president-elect himself, his treasury secretary (Steven Mnuchin), education secretary (Betsy DeVos) and commerce secretary (Wilbur Ross). Several other nominees are multimillionaires.
Icahn will help Trump deliver on his promises to deregulate the U.S. business climate. Both he and Trump have said they believe President Barack Obama's government has implemented too many corporate regulations that adversely affect the economy.