The actor also accused Trump of inappropriate behivour towards his wife Chynna Phillips at a party in a hotel in Manhattan.
Baldwin was replying to Trump's son, Donald Trump Jr, who posted a tweet about new allegations against embattled Democrat senator Al Franken.
"Your Dad is a 5th degree black belt when it comes to sexual impropriety allegations.
"In fact... I once had a party at the Plaza Hotel your father showed up uninvited and hit on my wife... invited her on his helicopter to Atlantic City," Baldwin tweeted.