Ferrán, 59, will be appointed non-executive director of the company on July 22, ahead of Humer's retirement.
Ferrán serves on the board of beer brewer SABMiller Plc as non-executive director and was earlier president and CEO at rum-maker Bacardi.
Shares in Diageo closed down 0.7 percent at 1843.5 pence on the London Stock Exchange on Wednesday.
(Reporting by Mamidipudi Soumithri in Bengaluru; Editing by Sriraj Kalluvila and Don Sebastian)