The team announced that Westbrook had the operation in a news release Saturday morning, stating that the All-Star would be re-evaluated in four weeks.
Thunder general manager Sam Presti told ESPN.com on Friday that Westbrook and the team, at that point, were undecided on whether Westbrook would have surgery on his hand, which he injured in Thursday's game against the Los Angeles Clippers.
Westbrook suffered a small break in the second metacarpal of his right hand when he inadvertently hit teammate Kendrick Perkins' elbow while going for a rebound.
The surgery was performed by Dr. Thomas Graham, who was assisted by Thunder medical personnel at the Cleveland Clinic.
The Thunder already had been attempting to account for the absence of reigning league MVP Kevin Durant, who is recovering from a foot injury and isn't expected to return until late November at the earliest.
Presti said Friday that the combined loss of Westbrook and Durant provides the Thunder's other players with an opportunity.
"The circumstances that we're being presented with right now are temporary," Presti said. "It's our job to eliminate the dramatics and harness our mentality and make sure that we're productively using the time so that when those guys do come back and we start to get our full complement of players, we have built a collective mentality and momentum that's only going to be accelerated when we get our group together."
The injury-ravaged Thunder also are without Mitch McGary (foot), Anthony Morrow (sprained MCL), Reggie Jackson (ankle), Jeremy Lamb (back) and Grant Jerrett (ankle). However, the team is optimistic both Lamb and Jackson can return in the upcoming week.
The Thunder are considering applying for a league hardship exception, which would allow them to sign an additional player to the roster because at least four players are out with injuries for a minimum of two weeks. Westbrook, Durant, Jerrett, McGary and Morrow all qualify under those requirements.
Teams can't apply for an exception until the players miss at least three games, meaning the Thunder can now make their application after Saturday's 102-91 win over the Denver Nuggets. Once Westbrook misses a third game, the Thunder then could apply for a second exception following their game against the Toronto Raptors on Nov. 4.
ESPN.com's Royce Young contributed to this report.