The procedure was performed by Dr. Jeff Yao on Friday at the Stanford Orthopaedic Surgery and Sports Medicine Clinic. While the team gave no timetable for his return, O'Neal thinks he can recover at some point this season.
"I am NOT out for the season contrary to some of the media reports," O'Neal wrote on Twitter, where he also posted photos of himself smiling at the hospital.
O'Neal, 35, is in his 18th NBA season and has had previous knee and wrist operations. He has appeared in 17 games this season, averaging 6.2 points, 4.5 rebounds and 18.6 minutes.
Warriors coach Mark Jackson declined to give a timeline for O'Neal's recovery before Friday night's home game against Houston, but he echoed his player's optimism.
"I believe that Dr. O'Neal wouldn't lie to us," Jackson said.
O'Neal is the third center behind starter Andrew Bogut to have surgery this year, leaving the Warriors' frontcourt severely short-handed.
Jackson said power forwards David Lee and Marreese Speights will spend some time at center. The Warriors also signed Hilton Armstrong, the former Connecticut center who was drafted 12th overall by New Orleans in 2006, from Santa Cruz of the NBA Development League on Wednesday.
O'Neal, who had emerged as a vocal leader in his short time with the Warriors, is expected to begin rehabilitation immediately.
"There's not much that he can do on the floor right now. But when he's able to, he'll be around this basketball team," Jackson said. "He's a big part of what we're doing moving forward."