The 30-year-old previously played for the Spanish club U.E. Llagostera. [Full schedule of ISL 2016]
Marcos is an academy product of Spanish giants Real Madrid. He only made one appearance for Real's senior side in the 2009-10 season before being loaned out.
"I'm very excited about this new stage in my career. I am looking forward to play for the Delhi Dynamos FC. I am sure ISL will be an enriching experience for me and I hope to take the maximum from it. My aim is to win the title this season with my new club," Marcos said in a release.
"I intend to learn a lot from head coach Gianluca Zambrotta. He's got immense experience, I am looking forward to working with him and the rest of the team."
Zambrotta was enthusiastic about his team's latest signing.
"Marcos is a very talented and experienced player. He has played against the top-flight clubs of Europe and his experience will be very useful for the team. He has an excellent tactical approach towards the game," said Zambrotta.