As if there was ever a question.
Duncan, 36, declared earlier this year that he was a "Spur for life" and this contract will likely represent the final deal of his certain first-ballot Hall of Fame career.
"Tim Duncan has established himself as one of the best players in NBA history," Spurs coach Gregg Popovich said in a statement. "His impact on the Spurs organization and the city of San Antonio can't be measured. We are all grateful for the leadership and dedication Tim has shown to the Spurs franchise. He is an unselfish superstar who loves to compete and has only one goal when he steps on the court – to do whatever it takes to help his team win. We are all thrilled that he'll spend his entire career as a San Antonio Spur."
Duncan averaged 15.4 points, 9.0 rebounds, 2.3 assists and 1.5 blocks last season. He helped lead the Spurs to the Western Conference Finals, where they lost to the Oklahoma City Thunder.
"I think (his health) probably had as much to do with solidifying in his mind how long he wanted to go into the future," Spurs GM R.C. Buford told The Associated Press. "He played well throughout this whole season and he even felt better than he ever had. I think in his mind, that was what was important. We're going to play him as long as he says he can play and then probably a couple of days longer."