Lionel Messi and Franck Ribery are the two other men in the running for the prize, but the striker has offered his support to the Real Madrid man
The race for this year's prize is the closest in years, with the Real Madrid and Portugal man - who was crowned the world's best player for the first time back in 2008 - joined on a three-man shortlist for award by four-time winner Lionel Messi and Franck Ribery.
A host of high-profile figures have offered their backing to all three candidates, with the winner of the trophy set to be announced at a ceremony in Zurich on January 13.
Speaking prior to the 'Champions for Life' charity match at the Santiago Bernabeu on Monday evening, a journalist quizzed Costa over his choice, to which the 25-year-old simply replied: "Cristiano."
Both Ronaldo and Costa have enjoyed sensational starts to the season and have scored a remarkable 37 Liga goals between them already.