The choice seemed fitting, since Clooney, no longer one of the world's most eligible bachelors, is also an Academy Award winner.
Photos published Tuesday of the private ceremony show the 36-year-old Alamuddin wearing an off-shoulder gown, hand-embroidered with pearls and diamante stones.
Alamuddin, a lawyer in Britain who's from a prominent Lebanese family, is said to have selected de la Renta from a number of designers who were vying for her attention.
"He’s such an elegant designer and such an elegant man,” Alamuddin told People.
Her 53-year-old groom wore a black Giorgio Armani tuxedo.
According to People, the wool-cashmere suit was accented by a gift from his bride: Personalized cuff links inscribed with "George" in Arabic.
The couple reportedly exchanged traditional vows, and a pair of platinum wedding bands, before a host of famous friends inside Venice's luxurious Aman Canal Grande hotel.
They followed it up with a civil ceremony before Italian authorities Monday afternoon.