Marcelo joined Real Madrid from boyhood club Fluminense as a prodigious 18-year-old in the winter transfer window of 2007, brought in as the long-term successor to his compatriot Roberto Carlos.
The Brazilian's current contract was valid until June 2020.
He has won 17 titles with Madrid, including three Champions Leagues and four Spanish leagues.
Marcelo given Real Madrid contract extension until 2022
Real Madrid midfielder Dani Ceballos isn't concerned about the lack of first-team action he is getting at his new club. "Tomorrow, Friday, at 14:00 h, Isco will appear before media in press room at Santiago Bernabéu stadium", according to press release by white club.
Casemiro revealed Real Madrid need Cristiano Ronaldo in the side at all times to help them win and score goals.
The contract news was announced for Marcelo shortly after he was given a two-match domestic ban by the Spanish federation (RFEF) for his sending-off in the 1-1 draw with Levante for kicking Jefferson Lerma in an off-the-ball incident.
The Brazilian International will be absent for Sunday's trip to Real Sociedad and the visit of Real Betis on September 20.More news: Catalan independence campaign kicks off as Barcelona gives backing