The 44-year-old actress announced her exciting news on Instagram after the ceremony. Moynahan looked gorgeous in a white sleeveless gown paired with a white fur stole, while her husband opted for a classy dark suit for the big day.
"Oh, by the way, guess what I just did @johndolanphotog," she captioned the photo.
Though the Hamptons wedding may come as a surprise, keeping mum is not unusual for the newlyweds. They have kept their relationship notably private after initially meeting through a mutual friend.
Prior to Frankel, Moynahan dated New England Patriots quarterback Tom Brady for three years before calling it quits in December 2006. The two have an 8-year-old son, John, together.
Just last month, Moynahan took to Twitter to share her support for Brady, following his victorious court appearance, in which a judge nullified his four-game suspension by the NFL. The football pro was originally put on suspension for his alleged role in using under-inflated footballs in a playoff game against the Indianapolis Colts last season.