George Clooney is an award-winning actor, a new father and a world-class prankster.

Now he can add “start-up founder who hit the jackpot” to his résumé.

Casamigos, the tequila brand that Mr. Clooney founded with his friends Rande Gerber and Mike Meldman in 2013, said Wednesday that it had sold itself to the spirits giant Diageo. 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.

“If you asked us four years ago if we had a billion-dollar company, I don’t think we would have said yes,” Mr. Clooney said in a statement. “This reflects Diageo’s belief in our company and our belief in Diageo.”

The transaction makes Mr. Clooney one of the most successful celebrity investors around.

Hollywood stars over the years have often played venture capitalists on the side, taking stakes in an array of start-ups. Among them are Kevin Spacey and Leonardo DiCaprio, who have poured money into Casper, the mattress maker, and Justin Bieber, who has invested in Spotify. Ashton Kutcher may now be better known for his investments than for his IMDB entries, having taken stakes in what Crunchbase reckons are 61 start-ups, like Airbnb and Change.org.