Clooney started Casamigos in 2013 with friends, Rande Gerber and Mike Meldman, reported the BBC.
He told CNBC that he and his co-founders would, "still be very much a part of Casamigos. Starting with a shot tonight. Maybe two."
Diageo will pay $700m initially for the brand, with a further $300m due over ten years, linked to performance. The deal is expected to be finalised later this year.
Casamigos, a contraction of the Spanish words for "house of friends," started as private collection of tequilas meant just for the founders' friends and family.
However, in 2013, they were told by their distiller that due to the quantities they were consuming they had to get the brand licensed.
According to Gerber, the brand was the fastest growing ultra-premium tequila in the US last November.