The agency was long held by Autogrill, an airport duty free operator.
Autogrill will continue to hold the rights to sell in the airport and the new firm will only distribute in the rest of the island, a source familiar with the matter said.
The firm also had no plans to produce the products in Sri Lanka, the source said.
Among other brands owned by Diageo are Guinness and Baileys.
Ceylon Beverage Holdings recently changed its name from the earlier Ceylon Brewery.