The 18-year-old Marcelo has been presented by club chairman Ramon Calderon in a press conference and the club's website said the deal worth $9 million.

"Signing Marcelo is part of a bigger plan of bringing young and talented players as we work for the future of the club," Calderon was quoted as saying by Spanish media.

"His defensive strength and attacking agility caught the attention of sports director Peja Mijatovic."

Marcelo may be playing with Real Madrid reserves for the rest of this campaign before joining the first team starting from next season.

He is seen as the future replacement of compatriot and veteran defender Roberto Carlos, who has agreed terms for an extension one day earlier.

The 33-year-old international will stay with the Spanish capital side till 2008.