Icahn, 80, reaffirmed his support for Trump in a phone interview with CNBC Monday:
"Over my years I've listened to a lot of salacious talk in locker rooms, bachelor parties, etc. by a lot of high-level people, some of whom are now supposedly so outraged ... All I can do is refer to that great quote, 'Let he who has not sinned cast the first stone,'" he told CNBC.
A 2005 audio tape leaked Friday, in which Trump boasted about kissing and groping women, ignited a firestorm over the weekend.
Icahn has been a vocal supporter of Trump for months. He has argued that Trump would reduce regulations for US companies and referring to Democratic nominee Hillary Clinton's economic plan as a "mishmash of contradictions."
Donald Trump has said that if elected, he would make Icahn Treasury secretary.
Icahn initially declined the offer, but has since tweeted that he would accept the offer.