Black Cats boss Gus Poyet swooped for the 27-year-old Romanian, whose contract was not renewed by City at the end of the season.
Pantilimon said: "It is a great privilege and honour to join a club like Sunderland.
"They have an amazing history and tradition and, of course, passionate fans.
"When I left Manchester City it was important that I chose a club with good ambition and a manager who has the hunger and desire to take the team forward.
"After speaking with the boss, I knew this was the right place and he was the right man
I can't wait to start."
The 6ft 8ins Romanian has signed a four-year contract at the Stadium of Light
Pantilimon is expected to challenge Vito Mannone for the number one spot following the departure from the club of Keiren Westwood.
Pantilimon made 29 appearances in three years for the Barclays Premier League champions, including deputising for the out-of-form Joe Hart.
Sunderland's sporting director Lee Congerton told the club's official website: "Competition for places is healthy and brings out the best in players.
"We already have a great goalkeeper in Vito Mannone and another one now in Costel.
"Add to this youngster Jordan Pickford, who recently signed a long-term deal and we have a very strong stable of goalkeepers, which is vitally important in the top flight."
Pantilimon is Sunderland's third signing since their dramatic escape from relegation, following Billy Jones and Jordi Gomez to the north-east.
Source : PA
Source: PA