The 32-year-old goalkeeper has signed a three-year contract at the Etihad Stadium to provide competition for Joe Hart.
The 32-year-old flew into Manchester on Monday and completed a medical for a deal worth 8 million euros.
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The Argentine told the club's official website: "I am very happy and really looking forward to the start of preseason and performing well to help the team. This is a new challenge and a new league for me. I have been doing well in the previous years and my goal is to go on and hopefully perform at the same level for City.
"I know I am coming to a big club with a very good goalkeeper. City already have a great goalkeeper in Joe Hart but I will try and compete for the No.1 spot. I will do my best in the training sessions."
City has been seeking a new keeper to provide competition for Hart since Costel Pantilimon left for Sunderland earlier this summer.
He joins Bacary Sagna and Fernando in signing for Manuel Pellegrini's side this summer, with the acquisition of Brunu Zuculini soon to be confirmed.