The deal values the company at up to $1 billion: $700 million in cash upfront and up to $300 million more if it hits sales targets over the next decade, reported Los Angeles Times.
"If you asked us four years ago if we had a billion- dollar company, I don't think we would have said 'yes'. This reflects Diageo's belief in our company and our belief in Diageo.
"But we're not going anywhere. We'll still be very much a part of Casamigos. Starting with a shot tonight. Maybe two," Clooney, 56, said in a statement.
Diageo's other liquor brands include Johnnie Walker and Crown Royal whiskies, Smirnoff and Ketel One vodkas, Guinness stout and Captain Morgan rum.