The surgery is to repair a torn labrum in his shoulder. Dr. Lewis Yocum will perform the operation in Los Angeles. Teahen will leave for the procedure on Wednesday.
That will deprive the Royals of their hot-hitting young star and No. 3 batter for the last 3 1/2 weeks of the season.
"It wasn't an easy decision, but I think it's the right decision," Teahen said.
Teahen said his right shoulder had been a problem since the last month of the 2005 season. He and club officials finally decided last Friday to go ahead with the surgery.
"We talked to him about it," manager Buddy Bell said. "For him to be ready for Spring Training, it was best to do it now."
The Royals will not bring up hot prospect Alex Gordon, the third baseman at Double-A Wichita, or anyone else to replace Teahen, according to Bell.
"We're going to ask George [Brett] if he can come back," Bell said.
Esteban German and Jeff Keppinger will be used at third base, he said.
Teahen, knowing that this was his last game until next season, was hitless in four at-bats in the 5-0 victory Tuesday night over the New York Yankees.
Teahen finished with a .290 average. He also is leading the club in home runs, 18, and triples, seven, even though he played in just 109 of 140 games.
He had a month-long stay at Triple-A Omaha and came back on fire. Since his return on June 3, he batted .313 and knocked in 60 runs in 86 games. Although he has 14 errors, he didn't make any in his last 27 games and continued to throw well.
Although there hadn't been any obvious consequences of his shoulder problem, Teahen knew it eventually would have to be fixed. Meantime, he adjusted.
"I've figured out how to play through it," he said, "but it's wiser to shut it down."
Bell said that Teahen's loss would be felt more than on the field. He's become a clubhouse leader, notably for younger players fighting their way through problems.
"It's a real tough time to walk away from it because I'm playing well and the team is playing well," he said.