The terms of the multiyear pact weren't revealed but Yahoo! Sports said it was valued at $48 million over four years.
"We are very excited that Serge will continue as a core member of the Thunder for years to come," General Manager Sam Presti said in a written statement. "Serge personifies many of the traits that we value as an organization; he is a tireless and disciplined worker, an elite competitor and someone who treats his profession with the utmost focus."
Ibaka, 22, played for the Spanish Olympic team in London this summer.
He has been with the Thunder since he was drafted in the first round in 2008. He averaged 9.1 points and 7.5 rebounds per game last season.